ENGLISH LANGUAGE GRAMMAR - Correct English Writing & Speaking
English Speaking & Writing Topics: Parts of Speech, Passive Voice, Direct Indirect Speech
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1.1. Grammar and Effective Writing
All writing begins with ideas that relate to one another. An author chooses words that express the ideas and
chooses an arrangement of the words (syntax) that expresses the relationships between the ideas. Given this
arrangement of words into phrases, clauses, and sentences, the author obeys grammar and punctuation rules to
form a series of sentences that will impart the ideas.
English rules of grammar originated in antiquity, but over centuries have evolved according to usage and are still
changing today. Thus, grammar rules may change and may be inconsistent, but usually have a functional basis.
This functional attitude toward grammar, and punctuation, is described in Effective Revenue Writing 2 (Linton
1962). A rule of grammar or punctuation with a functional basis will not prevent effective statement of ideas, nor
will following all the rules ensure effective writing.
Effective writing requires good syntax, that is, an effective arrangement of sentence elements. Obviously, an
editor is responsible for ensuring that a consistent and correct set of grammar and punctuation rules have been
applied to a report (a process often called copy editing). However, language and substantive edits, as defined by
Van Buren and Buehler (1980), involve revision of sometimes perfectly grammatical sentences to improve
effectiveness of sentence structure. This chapter discusses grammar, and the next chapter concerns sentence
structure with emphasis on methods of revision.
According to Webster's Ninth New Collegiate Dictionary, grammar means "the study of the classes of words,
their inflections [changes in form to distinguish case, gender, tense, etc.], and functions in a sentence." An
abundance of good, detailed grammar, writing, and usage books are available. This chapter is not meant to be a
definitive grammar reference. It is intended to address grammatical problems often encountered in technical
documents and to indicate preference when grammar authorities do not agree. Please refer to the books cited in
the References section and others to complement and clarify the discussions that follow.
1.2. Nouns
Nouns change form to indicate case and number. The number of a noun is usually not a problem (though the
number of pronouns and verbs corresponding to the noun may be). The three possible cases are nominative,
objective, and possessive. In English, nominative and objective case nouns have the same form.
1.2.1. Possessive Case
At Langley, the preferred rules for forming possessives are as follows (G.P.O. 1984; and Rowland 1962):
· Form the possessive of a singular or plural noun not ending in s by adding 's.
· Form the possessive of a singular or plural noun ending in s by adding an apostrophe only:
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Singular Plural
man's men's
horse's horses'
Jones' Joneses'
· Form the possessive of a compound noun by adding 's to the end of the compound:
sister-in-law's home
John Doe, Jr.'s report
patent counsel's decision
· Indicate joint possession by adding 's to the last element of a series; indicate individual possession by adding 's
to each element:
Wayne and Tom's office (one office)
editor's, proofreader's, and typist's tasks
Some authorities (for example, Skillin et al. 1974; and Bernstein 1981) partially disagree with the second rule
above. They state that the possessive of a singular proper noun is formed by adding 's even when the noun ends
in s (for example, Jones's); however, a triple sibilant is always avoided (for example, Jesus').
1.2.2. Possessive of Inanimate Objects
In the past, the possessive case ('s) was not acceptable for inanimate nouns. Instead the preposition of was
preferred, that is, strength of the laminate rather than laminate's strength..
Exceptions to this rule were inanimate words representing a collection of animate beings (for example, company's
profits, university's curriculum) and words expressing measure or time (for example, 2 hours' work). Current
practice is to dispense with both the 's and the of (Skillin et al. 1974):
company profits
university curriculum
laminate strength
2 hours work
In fact, the use of 's on an inanimate object is no longer taboo, particularly if the object has some lifelike qualities
(Bernstein 1981):
computer program's name
Earth's rotation
Whether an 's can properly be added to an inanimate noun seems to be a matter of idiom. We would not say, for
example,
systems' analyst
table's top
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1.3. Pronouns
All pronouns must have an antecedent (the noun they replace) with which they agree in number, gender, and
person. In addition, some pronouns change form to indicate nominative, objective, and possessive case (for
example, he, him, his).
· An apostrophe is never used to form possessive case pronouns.
1.3.1. Antecedents
Most grammatical errors involving pronouns result from the lack of a clear antecedent. The following sentences
suffer from this problem:
He foresaw aircraft applications and thus emphasized rectilinear motions.
This causes complicated integral equations for other types of motion.
The boundary condition becomes a source term, which permits use of the
Green function.
Required surface pressures are obtained in several ways, for example,
from blade element theory or experimental measurements. Whatever the
technique, it is usually available.
In the first two sentences the pronouns this and which refer to the idea of the previous sentence or clause and do
not have a noun antecedent. The Writer's Guide and Index to English (Ebbitt and Ebbitt 1978) states that this
"broad reference" usage of pronouns is acceptable in "general" writing, but should be avoided in "formal"
writing. The danger of broad reference is that the antecedent (whether a noun or a clause) may not be clear. In the
second sentence above, which appears to refer to term. The following revisions would be preferable:
He foresaw aircraft applications and thus emphasized rectilinear motion.
This emphasis causes complicated integral equations for other types of
motion.
Because the boundary condition becomes a source term, the Green
function can be used.
In the third sentence, it is much too distant from its antecedent, pressures. Because of this distance, the pronoun
does not agree in number with its antecedent.
Bernstein (1981) discusses ambiguous or nonexistent antecedents under "Pronouns" and under particular words,
for example, "Each" and "None."
· Grammatical errors involving pronoun antecedents can be avoided very simply: check every pronoun for a clear,
appropriate antecedent and then ensure agreement between antecedent and pronoun.
1.3.2. Personal Pronouns
First person pronouns
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Tichy and Fourdrinier (1988) attribute the pervasiveness of passive voice in technical writing to evasion of first
person pronouns (I, we). In the early 1900's, first person pronouns were banished from technical writing to
obtain objectivity; however, Tichy and Fourdrinier effectively demonstrate that objectivity is not always attained.
Writing authorities no longer forbid, and sometimes encourage, the use of first person pronouns (CBE 1978; AIP
1978; Houp and Pearsall 1984; and Mills and Walter 1978). Thus, we in technical documents cannot be
condemned, particularly when the opinion of the author (and a research staff) is being expressed:
We believe that this effect is due to nozzle aspect ratio.
This use of we, meaning "I and others," should be distinguished from the editorial we, meaning "you readers and
I" (Ebbitt and Ebbitt 1982). In technical documents the editorial we is often used in mathematical presentations:
Now we define a recursive relation for the (k + l)th iteration:
X k ) -1
P = (X T
k +1
/k
Tichy and Fourdrinier (1988) recommend that the antecedent of we always be made clear. They also offer advice
on when to use first person pronouns and when not to.
Gender
Third person singular pronouns change form to indicate gender (he, she). When the pronoun could refer to either
sex or when the antecedent's sex is unknown, the masculine pronoun is grammatical. However, in recent years,
objections have been raised to this grammatical rule.
· It is preferred practice to avoid the masculine pronoun when the antecedent may be feminine. Often the
antecedent can be made plural:
An editor must have guidelines on which to base his
Poor revisions.
Editors must have guidelines on which to base their
Better revisions.
Or the wording of the sentence can be changed:
The listener may not fully perceive the sound because
Poor his ear has a critical summation time of 1 sec.
The listener may not fully perceive the sound because
Better the human ear has a critical summation time of 1 sec.
1.3.3. Relative Pronouns
Relative pronouns function not only as pronouns but also as conjunctions. The relative pronoun replaces a noun
in a dependent clause and connects the clause to the rest of the sentence.
Antecedents of relative pronouns
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· Who and whom refer to persons.
· Which refers to things.
· That refers to things and in rare instances may refer to persons.
· Whose, the only possessive case relative pronoun, may refer to either persons or things according to Bernstein
(1981). Other grammar authorities disagree and condemn the use of whose to refer to inanimate nouns. We prefer
whose when of which would be awkward:
A low-cost process has been developed for making alumina,
Awkward
the limited availability and cost of which have previously
inhibited its widespread use.
A low-cost process has been developed for making alumina,
Better
whose limited availability and cost have previously inhibited
its widespread use.
The attenuation is accompanied by an echo the amplitude
Awkward
of which is above the background level and the position of
which is related to the depth of the region.
The attenuation is accompanied by an echo whose amplitude
Better
is above the background level and whose position is related
to the depth of the region.
Which versus that
· Which is always used in a nonrestrictive relative clause (one that could be omitted without changing the meaning
of the basic sentence):
The most common examples of panel methods are the aerodynamic codes of Hess and Smith (ref.
26), which were originally developed for nonlifting surfaces.
Which may also be used in a restrictive relative clause. Note that proper punctuation of restrictive and
nonrestrictive clauses is vital: commas enclose nonrestrictive clauses, but never enclose restrictive clauses (see
section 3.5.2).
· That is preferred for restrictive (or defining) relative clauses (Bernstein 1981):
The most common examples of panel methods are the aerodynamic codes that Hess and Smith
(ref. 26) designed for nonlifting bodies.
There are three exceptions to the use of that to introduce a restrictive clause:
· Which must be used after a preposition (Bernstein 1981):
The shading in figure 2 indicates elements in which fibers have failed.
· Which is used after the demonstrative that (Bernstein 1981):
The most commonly used aerodynamic code is that which Hess and Smith (ref. 26) designed for
nonlifting bodies.
· Which sounds more natural when a clause or phrase intervenes between the relative pronoun and its antecedent
(Fowler 1944):
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Finite bodies can undergo motions (such as spinning) which complicate the equations.
Omission of that
That can sometimes be omitted from restrictive relative clauses, but this omission is not recommended:
Correct The model they analyzed is the most realistic one studied.
The model that they analyzed is the most realistic one
Better studied.
Who versus whom
Who (and its indefinite derivative whoever) is the only relative pronoun that changes form to indicate case (who,
whom, whose). When a relative clause is inverted, we have difficulty determining whether the pronoun is in
nominative case (who) or in objective case (whom). The easiest way to resolve such questions is to change the
relative clause to an independent clause by substituting a third person personal pronoun for the relative pronoun.
For example, in the questionable sentence
Information derived from this contract may be transmitted to those who the Defense Department
has cleared to receive classified information.
change the relative clause to an independent clause:
The Defense Department has cleared them to receive classified information.
The sentence requires a third person pronoun in objective case (them), so the relative pronoun must also be in
objective case (... those whom the Defense ... ).
1.3.4. Demonstrative Pronouns
Demonstrative pronouns refer to something present or near (this, these) or to something more remote (that,
those). Technical writing tends to exhibit two types of problems involving demonstrative pronouns: broad
reference (see section 2.2.1) and incomplete comparison (see section 2.5.2).
Broad reference
The demonstrative this is often used to refer to the idea expressed in the previous sentence, a practice to be
avoided in formal writing (Ebbitt and Ebbitt 1982). For example,
The entire noise prediction methodology for moving bodies becomes autonomous. This means
that improved models can be incorporated simultaneously in pressure and noise calculations.
Most loads could be reduced 0.8 percent if voltage was more closely regulated. Nonessential loads
such as payloads could take advantage of this, but essential loads could not.
This type of construction is sometimes vague and usually unnecessary. Often the demonstrative pronoun can be
deleted:
The entire noise prediction methodology for moving bodies becomes autonomous. Thus,
improved models can be incorporated simultaneously in pressure and noise calculations.
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Or the antecedent can be clarified:
Most loads could be reduced 0.8 percent if voltage was more closely regulated. Nonessential loads
such as payloads could take advantage of voltage regulation, but essential loads could not.
Incomplete comparison
Demonstrative pronouns can often be used to complete vague comparisons:
Poor The errors in this prediction are greater than in table III.
The errors in this prediction are greater than those in table
Better III.
But make sure that the antecedent and meaning are clear:
West's results were in better agreement with ours than those
Unclear
of Long et al.
West's results were in better agreement with ours than those
Either
of Long et al.
West's results were in better agreement with ours than with
Or
those of Long et al.
See section 2.5 for further discussion of comparisons.
1.4. Verbs
Verbs, the only words that can express action, change form to indicate person, tense, mood, voice, and number.
1.4.1. Tense
Verbs change form to indicate tense, or time that an action or state of being takes place. English has six tenses:
present, present perfect, past, past perfect, future, and future perfect. Each of the six tenses has a progressive
form indicating a continuing action. (See Text 4 of Effective Revenue Writing 1, IRS 1962.) Writing authorities
do not specify exactly which tenses should be used in a technical document, but they universally agree that shifts
in tense should occur only when the time of the action changes. In other words, the point of view of a report with
respect to tense must be consistent.
The relationship between point of view and verb tense can be understood in terms of the four elements of
discourse (Buehler 1970):
Exposition (explains how and why things happen)
Narration (tells what happened)
Description (gives a mental image)
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Argumentation (convinces by reasoning)
The elements are quite often mixed. For example, in the Results and Discussion section, behavior of models or
specimens (narration) might be discussed alang with presentation of results in tables and figures (description) and
explanation of results (exposition). Narration is usually in past tense while description and exposition are usually
in present tense. Consistency in tense does not mean that all sentences are in the same tense; it means that
sentences expressing the same point of view (or element of discourse) are in the same tense. Avoid shifting back
and forth between points of view by grouping material with a consistent viewpoint; but when the viewpoint does
shift, shift the tense accordingly.
Tenses of independent clauses of report
There are no firm rules concerning tense of various sections in a report. However, if an author is inconsistent in
tense, the following guidelines might be helpful to the editor:
· The Summary is usually in past tense.
· Past research (for example, in references) is usually described in past tense.
· Permanent facilities are usually described in present tense.
· Experimental procedures and apparatus for a particular study are usually described in past tense.
· Behavior of models, specimens, etc., during the study is usually expressed in past tense, and results presented
in the report's illustrative material are expressed in present tense:
Typical fracture profiles are shown in figure 21. These profiles show that fracture mode changed
with cyclic exposure. The specimens failed ...
As shown in figure 10, the autorotative rolling moment is a nonlinear function of roll rate, so that
as spin rate increased, the propelling moments became equal.
· Explanation of why results occurred are in present tense:
The data failed to provide any reasonable estimates for Cnr. This failure can be attributed to the
small excitation of yawing velocity.
· The Concluding Section is usually in past tense except that conclusions (that is, deductions thought to be
universally true independent of the specific conditions of the investigation) should be in present tense.
· The Abstract is usually in present tense.
Sequence of tenses
The logical time relation between the various verbs and verbals in a sentence is expressed by shifts in the tense of
these verbs and verbals. Sequence of tenses is a very complicated subject, which is discussed in almost every
grammar and writing book. Only the basic guidelines are given here; for a more complete understanding, refer to
such reference books.
· When the principal verb is in a present or future tense, subordinate verbs may be in any tense:
The data indicate that lift increases with angle of attack up to = 35°.
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The data indicate that the specimen failed in a noncumulative mode.
The data indicate that propellers will have a place as a propulsive device of the future.
· When the principal verb is in a past tense, the subordinate verb must be in a past tense unless the subordinate
clause expresses a universal truth or an action that is still continuing:
The data indicated that lift increased with angle of attack up to = 35°.
Previous studies had indicated that alumina is a suitable fiber for reinforcement.
· The present tense forms of verbals refer to action occurring at the same time as the main verb; the past tense or
perfect tense forms of verbals refer to action occurring before the action of the main verb. This principle is most
easily seen for participles:
Photographs indicating nearly laminar flow justified this assumption.
Photographs taken during an earlier test justified this assumption.
1.4.2. Mood
The three moods in English are indicative, imperative, and subjunctive. Almost all verbs in technical documents
are indicative. Imperative mood is sometimes used in instructions or descriptions of procedures. Subjunctive
mood is rarely used and seems to be disappearing from English usage. However, there are two situations when
the subjunctive should be used (Bernstein 1981):
· Subjunctive mood is used to indicate a command, suggestion, recommendation, or requirement:
The console operator instructed that the preflight inspection be repeated.
The committee recommends that this research be continued.
· Subjunctive mood is used to indicate a condition contrary to fact or highly improbable:
If the integral were not singular, the question could be solved easily.
Up to now, all discontinuous fiber-reinforced composites have low ductility. If their ductility were
improved, they would be highly attractive materials for aircraft applications.
The subjunctive should be used only when the author wishes to imply strong doubt. Notice the subtle change in
attitude when the subjunctive is not used in the above example:
If their ductility was improved, they would be highly attractive materials for aircraft applications.
1.4.3. Voice
The voice of a verb indicates whether the subject is performing the action (active) or receiving the action
(passive). Writing authorities overwhelmingly prefer active voice because it is direct, clear, and natural. Overuse
of passive voice weakens style and obscures responsibility. This preference for active voice is not a
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condemnation of passive voice. Tichy and Fourdrinier (1988) list five situations when the passive voice is
appropriate:
· When the actor is unimportant, not known, or not to be mentioned
· When the receiver of the action should be emphasized
· When the sentence is abrupt in active voice
· When variety is needed in an active voice passage
· When a weak imperative is needed (for example, "The figures should be corrected quickly" )
The first two items justify much of the passive voice in technical documents. See section 2.2.2 for a discussion of
revising passive voice sentences to make them active voice.
1.4.4. Verb Number
A verb must agree in number with its subject. This is a simple and absolute rule. However, verb-noun
disagreements (in number) are common grammatical errors, sometimes caused by words intervening between the
subject and verb and sometimes caused by difficulty in determining the number of the subject.
· Some nouns have confusing singular or plural forms, for example,
aeronautics, sing. equipment, sing.
apparatus, sing. hardware, sing.
apparatuses, pl. phenomena, pl.
1 criteria, pl.
data, pl.
Consult the dictionary or a usage book when there is a question concerning the number of a particular noun.
Subjects joined by coordinate conjunctions
· Subjects joined by and, whether singular or plural, require a plural verb.
· Singular subjects joined by or or nor require a singular verb.
· When a singular subject and a plural subject are joined by or or nor, the verb agrees in number with the subject
nearer to it.
· When subjects are joined by and/or, the number of the verb depends on the interpretation of and/or. Either a
singular or plural verb can be justified. Bernstein ( 1981 ) considers and/or a "monstrosity" and recommends that
it be avoided. Often either and or or alone is sufficient.
Authorities disagree on the number of the noun data. Bernstein (1981) takes the traditional view that it is a plural
noun, but Tichy and Fourdrinier (1988), Ebbitt and Ebbitt (1982), and IRS (1962) consider it to be a collective noun
either singular or plural depending on its meaning. We prefer that data be plural in Langley reports.
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Subjects with intervening phrases
Phrases that intervene between the subject and verb do not affect number of the verb; it always agrees with the
subject:
Damping ratio as well as frequency agrees with the experimental values.
This error plus any other systematic errors appears in the output of the instrument.
Collective subjects
A singular collective subject, which names a group of people or things, is treated as singular when the group is
considered a unit or as plural when the members of the group are considered individually:
Langley's research staff is well-known for its achievements in aeronautics.
Langley's research staff do not all publish their results in report form.
· The number of such words as most, all, some, half, part, or percent is governed by the number of the noun in
the phrase that follows, or that could follow, them:
Most of the measurements contain this error.
Most of the disagreement between the plots is attributed to this error.
Six percent of the chord has laminar flow.
Of the subjects tested, six percent rate all the noises acceptable.
· When a number is used with a plural noun to indicate a single measurement, a singular verb is required:
Twenty liters of fuel has passed through the combustion system.
When such a subject is thought of as individual parts, a plural verb is appropriate:
Twenty milliliters of water were added, one at a time, to the solution.
Compound clauses with auxiliary verbs omitted
In compound sentences with passive voice verbs, the auxiliary verbs are sometimes erroneously omitted:
The wing plate was fabricated from nickel 201, its surface polished, and nickel rods welded to its
edge.
· The omission of auxiliary verbs is grammatical unless the subjects change number (Rowland 1962). The above
sentence should be
The wing plate was fabricated from nickel 201, its surface polished, and nickel rods were welded
to its edge.
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1.5. Adjectives
Since modifiers make up the bulk of most writing, their placement is very important to sentence structure.
In contrast to adverbs, adjectives are naturally placed near the noun or pronoun that they modify. Single-word
adjectives and unit modifiers precede the noun and adjective phrases and clauses follow it. See section 2.2.3 for a
discussion of placement of modifiers.
See section 2.5.1 for discussion of the degree (positive, comparative, and superlative) of adjectives.
1.5.1. Articles
Indefinite articles a and an
· The indefinite article a precedes a word beginning with a sounded consonant, and an precedes a word beginning
with a vowel sound.
· Whether a or an should precede an abbreviation or acronym depends not on its initial letter but on how the
author expects it to be read (Bernstein 1981). For example, most people read "M.A." as letters rather than as
"Masters of Arts," so "an M.A. degree" is appropriate. Likewise, we prefer "an NACA airfoil." However,
"NASA" is not usually read as letters, so we prefer "a NASA airfoil."
Articles with coordinate adjectives
Whether or not articles are repeated before coordinate adjectives affects meaning (Rowland 1962).
· If coordinate adjectives each refer to different things or persons, articles are repeated when the modified noun is
singular and are not repeated when the modified noun is plural:
The transverse and shear strain is calculated for each
Wrong specimen. (two strains)
The transverse and the shear strain is calculated for each
Correct specimen.
The transverse and shear strains are calculated for each
Or specimen.
· If coordinate adjectives refer to one thing or person, the article is not repeated:
A more nonlinear and a lower stress-strain curve resulted
Wrong from the test. (one curve)
A more nonlinear and lower stress-strain curve resulted
Correct from the test.
Omission of articles
There is a trend in modern writing, particularly journalism, to omit articles. Langley has traditionally preferred
this "elliptical style" for symbol lists, figure captions, headings, and titles:
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ratio of [the] wing mass to [the] mass of air in [a] truncated cylindrical cone enclosing [the]
wing
Figure 1. Effect of leak area on pressures, heating rates, and temperatures in [the] cove and at
[the] bulkhead.
Spectral Broadening by [a] Turbulent Shear Layer
Bernstein (1981) calls elliptical style a "disfigurement of the language." The author, or editor, may prefer to retain
(or restore) articles in symbol lists, figure captions, headings, and titles.
1.5.2. Unit Modifiers
Technical writing abounds with unit modifiers, that is, combinations of words that modify another word:
The annular suspension and pointing system for space experiments is described.
These values identify the beginning of shock wave boundary layer interaction.
Separated flow wing heating rate values increase sharply toward a constant value.
Authors and editors often have difficulty deciding when and how to hyphenate these modifiers. Bernstein (1981)
considers hyphens a necessary evil to be used only to avoid ambiguity. Certainly, unit modifiers need not always
be hyphenated and hyphenation does not always prevent ambiguity.
Before agonizing over hyphenation of these modifiers, consider changing them to prepositional phrases to clarify
their meaning. Perhaps this change only a few times in a report is sufficient to clarify the unit modifier when it
appears subsequently.
Surely the prepositional phrases in the following sentences are clearer than the hyphenated unit modifiers:
Unit The annular suspension-and-pointing system for space
modifier experiments is described.
Prep. The annular system for suspension and pointing of space
phrase experiments is described.
Unit These values identify the beginning of shock-wave-
modifier boundary-layer interaction.
Prep. These values identify the beginning of interaction between
phrase the shock wave and boundary layer.
Unit Separated-flow wing heating-rate values increase sharply
modifier toward a constant value.
Prep. Heating rates on the wing over which the flow is separated
phrase increase sharply toward a constant value.
Too many prepositional phrases can make the sentence awkward and hard to read, as in the last example. The
following might be preferable:
Separated-flow heating rates on the wing increase sharply toward a constant value.
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Probably the best authority on hyphenation of unit modifiers is the G.P.O. (1984). Unfortunately we sometimes
forget rule 6.16:
Where meaning is clear and readability is not aided, it is not necessary to use a hyphen to form a
temporary or made compound. Restraint should be exercised in forming unnecessary
combinations of words used in normal sequence.
· A unit modifier should not be hyphenated
When the unit modifier is a predicate adjective: The aircraft was flight tested.
Note: that an adjective that is hyphenated in the dictionary is hyphenated as a predicate adjective (IRS
1962): The method is well-known.
When the first element of the unit modifier is a comparative or superlative: higher order calculations
When the first element is an adverb ending in ly: relatively accurate prediction
When the unit modifier is a foreign phrase: a priori condition
When the unit modifier is a proper name: North Carolina coast (but Anglo-American plan)
When the unit modifier has a letter or number designation as its second element: material 3 properties
When the unit modifier is enclosed in quotation marks: "elliptical style" symbol list
When the unit modifier is a scientific name of a chemical, an animal, or a plant which is not normally
hyphenated: nitric oxide formation
· A unit modifier should always be hyphenated
When the unit modifier contains a past or present participle: flight-tested model, decay-producing moment
When the unit modifier is a combination of color terms: blue-gray residue
When a connecting word is implied in the unit modifier: lift-drag ratio, Newton-Raphson iteration
When the unit modifier contains numbers (other than number designations): three-degree-of-freedom
simulator, 0.3-meter tunnel
Note: we prefer that a number and unit of measurement not modify the quantity measured:
Poor 3° angle of attack
Correct angle of attack of 3°
Poor 15 000-ft altitude
Correct altitude of 15 000 ft
Of course, there are many instances other than those listed above when a unit modifier may be hyphenated. See
Skillin et al. (1974) and G.P.O. (1984) for discussions of permissible temporary compound words. The above
guidelines are based on the hyphenation rules proposed by Murdock (1982). She attempted to eliminate the need
for subjective decisions concerning the clarity of unit modifiers. Unfortunately, her rules do not always ensure
clarity. It seems that authors and editors must subjectively decide whether or not a unit modifier is clear and
readable without a hyphen.
1.6. Adverbs
Adverbs modify verbs, adjectives, and even other adverbs, but not nouns or pronouns. Adjectives can modify
only nouns and pronouns. Grammatical errors sometimes occur when an adjective tries to modify a verb:
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Wrong The balance was mounted internal to the model.
Correct The balance was internally mounted on the model.
Or The balance was mounted inside the model.
Note the position of the adverb internally in the above example. The natural place for a single-word adverb is
within the verb phrase. However, some adverbs can be moved within a sentence to change emphasis (see section
2.6). Although adverbial words and phrases can be moved easily within a sentence, they can be misplaced when
their modification is not clear.
See section 2.5.1 for discussion of degree (positive, comparative, and superlative) of adverbs.
1.6.1. Misplaced Adverbs
Some adverbs such as only, almost, nearly, also, quite, merely, and actually must be placed as close as possible
to the words that they modify (see the discussion of "only" in Bernstein 1981):
Misplaced The approximation is only valid for u = 0.
Correct The approximation is valid only for u = 0.
Misplaced The flow had separated nearly over the whole wing.
Correct The flow had separated over nearly the whole wing.
It is only necessary to apply equations (6) to (12) to
Misplaced
compute D.
It is necessary to apply only equations (6) to (12) to
Correct
compute D.
1.6.2. Squinting Adverbs
An adverb "squints" when it is not clear whether it modifies the preceding or the following words:
Although the operator eventually replaced the thermocouple,
Squinting
during that test, the temperature measurements were
inconsistent.
Although during that test, the operator eventually replaced
Either
the thermocouple, the temperature measurements were
inconsistent.
Although the operator eventually replaced the thermocouple,
Or
the temperature measurements were inconsistent during that
test.
1.6.3. Split Infinitives
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Despite the fact that split infinitives have usually been proscribed in formal writing, most, if not all, grammar
authorities recommend splitting an infinitive to avoid ambiguity or awkwardness. In particular, do not place an
adverb before or after an infinitive if in that position the adverb might appear to modify a word other than the
infinitive:
He agreed to immediately recalibrate the surface pressure
Split
instrumentation on the wing.
He agreed immediately to recalibrate the surface pressure
Squinting
instrumentation on the wing.
He agreed to recalibrate immediately the surface pressure
Awkward
instrumentation on the wing.
Split The flow at = 0° was the first to completely establish itself
over the wing.
Awkward The flow at = 0° was the first completely to establish itself
over the wing.
Squinting The flow at = 0° was the first to establish itself completely
over the wing.
· Avoid splitting an infinitive with a phrasal adverb. Such split infinitives are usually awkward.
1.7. Prepositions
Prepositions are handy little words that connect a phrase to a sentence and at the same time impart meaning.
Prepositional phrases can function as adjectives, adverbs, or nouns.
When prepositions are used redundantly or unnecessarily, they should be deleted for the sake of brevity (see
section 2.4.1).
1.7.1. Prepositional Idioms
Choosing the right preposition to use in a particular construction is a matter of idiomatic usage, not governed by
grammatical rules. Therefore, when questions arise concerning prepositional idioms, consult the dictionary, a
usage reference (such as Bernstein 1981), or a list of such idioms (Skillin et al. 1974 and Rowland 1962 contain
sections entitled "The Right Preposition" ). Some examples of prepositional idioms follow:
analogous to correlation with
attempt (n.) at implicit in
attempt (v.) to similar to
coincident with theorize about
different from variance with
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1.7.2. Terminal Prepositions
Most authorities agree that ending a sentence with a preposition is grammatical, although they often recommend
avoiding terminal prepositions because sentences should end with strong words rather than weak ones (see
section 2.6 for positions of emphasis in a sentence). If deleting a terminal preposition results in an awkward
sentence or changes emphasis in the sentence, nothing has been gained:
Term. prep. This hypothesis is intuitively difficult to disagree with.
This is an intuitively difficult hypothesis with which to
Awkward disagree.
Change emphasis To disagree with this hypothesis is intuitively difficult.
Bernstein (1981) provides an excellent discussion of this topic. He summarizes by stating, "If by trying to avoid
ending a sentence with a preposition you have seemed to twist words out of their normal order and have created a
pompous-sounding locution, abandon the effort."
1.7.3. Repeating Prepositions
Prepositions must be repeated in coordinate phrases only when they are required for clarity or when their
omission breaks rules of parallelism:
Unclear Shock tests were conducted in nitrogen and oxygen.
Either Shock tests were conducted in nitrogen and in oxygen.
Shock tests were conducted in a mixture of oxygen and
Or nitrogen.
Not parallel Tests were conducted not only in nitrogen but also oxygen.
Test were conducted not only in nitrogen but also in
Correct oxygen.
Of course, prepositions (and articles) can be repeated for emphasis.
1.8. Conjunctions
Conjunctions are classified as coordinating, joining sentence elements of equal grammatical rank, and as
subordinating, joining elements of unequal rank.
1.8.1. Coordinating Conjunctions
Coordinating conjunctions join grammatically equal sentence elements; that is, they join a word to a word, a
phrase to a phrase, or a clause to a clause. They thus provide important opportunities to use parallelism. See
section 2.3 for a discussion of parallel construction. The three types of coordinating conjunctions are:
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Coordinate conjunctions: and, but, or, nor
Correlative conjunctions: either ... or, both ... and, not only ... but also
Conjunctive adverbs: therefore, however, thus, hence, otherwise
Coordinate conjunctions
Coordinate conjunctions can join words, phrases, and clauses. The elements that they join must be equal
grammatically. A coordinate conjunction cannot join a noun and prepositional phrase, for example:
Pressures at the bulkhead, the seal, and in the cove are
Wrong shown.
Pressures at the bulkhead, at the seal, and in the cove are
Correct
shown.
Nor can a coordinate conjunction join a noun and a clause:
Notable characteristics of the air duct system are the
Wrong
acoustic treatment of the ducts and that the compressor can
force flow both ways through the system.
Notable characteristics of the air duct system are the
Correct
acoustic treatment of the ducts and the ability of the
compressor to force flow both ways through the system.
Correlative conjunctions
Correlative conjunctions are pairs of words that connect parallel sentence elements.
· Each member of the correlative must be followed by the same part of speech
The microprocessor provides both radiometer control
Wrong
functions and formats the data.
The microporcessor both controls the radiometer and
Correct
formats the data.
Also it is good practice to keep elements joined by correlatives strictly parallel:
The subsystem not only measures temperature but it also
Poor
provides real-time displays.
The subsystem not only measures temperature but also
Better
provides real-time displays.
This duct serves either as an eductor that provides an exit to
Poor
the atmosphere or as an inductor sucking air into the
system.
This duct serves either as an eductor exiting air to the
Better
atmosphere or as an inductor sucking air into the system.
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Conjunctive adverbs
Conjunctive adverbs can be used to join independent clauses only. In contrast to coordinate conjunctions,
conjunctive adverbs have more modifying character and less connective force.
· Clauses joined by conjunctive adverbs must be separated by a semicolon (or a period):
The differences were generally about 11 percent, but larger
Coord. conj.
differences occurred at = 15°.
The differences were generally about 11 percent; however,
Conj. adv.
larger differences occurred at = 15°.
1.8.2. Subordinating Conjunctions
Subordinating conjunctions connect dependent clauses to independent clauses. They are discussed in three
categories:
Adverbial conjunctions, which join adverbial clauses to independent clauses: for example,
because, though, after, where, so that.
Relative pronouns, which are discussed in section 1.3.3.
That, which is used as a function word to introduce dependent clauses.
Adverbial conjunctions
Subordinating conjunctions that join adverbial clauses to independent clauses are called adverbial conjunctions.
The biggest problem with these conjunctions is deciding whether the dependent clause is restrictive or not in order
that the sentence can be properly punctuated (see section 3.5.2).
Some of these conjunctions are often used improperly:
· As, since, and while have meanings other than those involving time, so that care must be taken to ensure that
their meaning is clear.
· If introduces clauses indicating condition; whether introduces clauses indicating alternatives:
Aerodynamic forces were studied on a two-dimensional
Wrong
wing section to determine if similar trends would be
calculated.
Aerodynamic forces were studied on a two-dimensional
Correct
wing section to determine whether similar trends would be
calculated.
· Where refers to place or location. It is often used incorrectly to replace that, when, or a relative pronoun:
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This formulation is equivalent to the Prandtl-Glauert
Wrong
transformation, where the body is stretched to correct for
the actual distance.
This formulation is equivalent to the Prandtl-Glauert
Correct
transformation, by which the body is stretched to correct for
the actual distance.
· While used in the sense of although or whereas is becoming accepted, with reservation. Skillin et al. (1974)
approve of using while to mean although so long as its use "does not defy the sense of at the same time."
Bernstein (1981) describes this usage of while as acceptable, "but with less universal sanction."
For a better understanding of these or other usage problems, consult Bernstein (1981) or other usage references.
The subordinating conjunction that
The subordinating conjunction that is defined in the dictionary as a function word that introduces several types of
dependent clauses, for example, noun clauses:
That the seven-term function does not result in a good approximation is apparent.
· That may sometimes be omitted in noun clauses (particularly following such verbs as say, think, and believe),
but this omission is not recommended:
The listeners believe the noise might hurt them.
Correct
The listeners believe that the noise might hurt them.
Better
The computation is adequate provided it is converged with
Correct
respect to collocation order.
The computation is adequate provided that it is converged
Better
with respect to collocation order.
· When a phrase or clause intervenes between that and the rest of the dependent clause, that is sometimes
incorrectly repeated:
He concluded that because checks were made with 128
Wrong
collocation points and only small differences were found,
that the results shown were converged.
He concluded that because checks were made with 128
Either
collocation points and only small differences were found,
the results shown were converged.
Because he made checks with 128 collocation points and
Or
found only small differences, he concluded that the results
shown were converged.
1.9. Verbals
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The three types of verbals are the gerund (verb ending in ing used as a noun), the participle (verb used as an
adjective), and the infinitive (verb preceded by to used as an adverb, adjective, or noun).
1.9.1. Coordinate Gerunds and Infinitives
Grammar authorities all remind us that a gerund takes a singular verb:
Substituting the expression into equation (2) yields ...
But these authorities are silent on the number of a verb following coordinate gerund subjects:
Substituting this expression in equation (2) and simplifying the result yields . . .
· We prefer a singular verb if a series of actions expressed by coordinate gerunds can be considered a single
process.
· Likewise, the prepositions should not be repeated before coordinate gerunds or infinitives that express a process
(Rowland 1962):
The following expression results from substituting equation (1) into equation (2), integrating by
parts, and taking the limit.
The test procedure was to combine the samples in a large vat, stir the mixture, and then withdraw
samples for analysis.
See section 1.7.3 concerning repetition of prepositions in coordinate phrases.
1.9.2. Idiom Requiring Gerund or Infinitive
Whether a particular verb should be followed by an infinitive or a gerund phrase is a matter of idiom, for
example,
The display helped the pilot to cope with the increased work
Correct
load.
The display aided the pilot to cope with the increased work
Wrong
load.
Although the meaning of these two sentences is the same, changing the verb changes the verbal required by
idiom:
The display aided the pilot in coping with the increased
Correct
work load.
Consult a usage reference (for example, Skillin et al. 1974) to check for these idioms; the dictionary also offers an
indication of idiomatic usage.
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1.9.3. Dangling Verbals
An infinitive, gerund, or participle dangles when the agent of the action that it expresses is not clear.
Some authorities (IRS 1962; Tichy and Fourdrinier 1988) consider an introductory gerund or infinitive phrase to
dangle when it does not modify the subject:
When using a nonaligning pitot static tube, the total velocity component cannot be exactly
measured because of the swirl component.
To predict the thrust and power coefficients of the propeller, the aerodynamic coefficients must be
provided.
Rowland (1962) considers such gerund phrases acceptable because "they are employed so frequently in technical
writing that they may be said to be idiomatic." The same can be said of introductory infinitive phrases. These
introductory phrases are clearly adverbial because no one would attribute their action to the subject. Note that the
verbs in the above sentences are in passive voice, so that an unknown agent can be supplied for the verbals'
actions. When the verb is in active voice, the verbal tends to dangle:
When using a nonaligning pitot probe, the swirl component precludes exact measurement of total
velocity.
· Introductory gerund and infinitive phrases do dangle when they modify a noun in the sentence other than the
subject:
When using a nonaligning pitot static tube, total velocity
Wrong
cannot be measured exactly by the investigator because of
the swirl component.
When using a nonaligning pitot static tube, the investigator
Correct
cannot exactly measure total velocity because of the swirl
component.
Although Rowland justifies introductory adverbial gerund and infinitive phrases because they are idiomatic and
clearly adverbial, he does not extend this argument to participles. He condemns dangling participles as "slovenly
English" and "weak constructions that should be replaced by more robust phrasing." Are dangling participles
slovenly English? Or, like the dangling gerund, are they becoming idiomatic?
Absolute participles
A class of apparently dangling participial phrases that have become idiomatic are absolute participles (Bernstein
1981). They have no antecedent and none is intended; that is, they are indefinite, for example,
The density mode is preferred provided that optical properties are measured.
Given a variable factor, the fluctuating flow components can be calculated from equations (31) to
(38).
Either the density mode or the pressure mode can be used, depending on whether supporting
optical measurements or probe measurements are made.
Other idiomatic absolute participles are
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generally speaking concerning
considering regarding
judging beginning
Such constructions must be truly absolute, with no antecedent in the sentence. In the following sentence, what
appears to be an absolute participle is actually dangling:
An arbitrary factor controls the accuracy of the calculation
Dang. partic.
depending on pressure fluctuations.
A variable factor depending on pressure fluctuations
Better
controls the accuracy of the calculation.
Technical writing often contains absolute participles that are not idiomatic, for example,
The arbitrary factor can be assumed to be small and therefore can be neglected, yielding a first-
order solution.
Such a participle might be justified by arguing that it is an absolute adjective construction modifying the whole
sentence. However these participles can sometimes be made adverbial:
The arbitrary factor can be assumed to be small and therefore can be neglected to yield a first-order
solution.
Sometimes a participle at the end of a sentence is not absolute, but actually modifies the subject in a nonrestrictive
way:
Nonrestrictive partic. Increasing the leak area caused the boundary layer to attach,
thus decreasing heat transferred to the cove interior.
The MLA's Line by Line (Cook 1985) does not object to such placement of a participle. However, these
participles can usually be changed to a compound predicate:
Compound predicate Increasing the leak area caused the boundary layer to attach
and thus decreased heat transferred to the cove interior.
Do not confuse absolute participles with nominative absolute constructions, which are perfectly grammatical.
Nominative absolutes have their own subjects and modify the whole sentence:
Maraging steels are promising for cryogenic service, having
Dang. partic.
hardness at -320°F of 38R c.
Maraging steels are promising for cryogenic service, their
Nom. abs.
hardness at -320°F being 38R c.
Adverbial participles
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What appears to be a dangling participle is left when the preposition by is dropped from an adverbial gerund
phrase. These "adverbial participles" may appear after the verb or at the beginning of the sentence:
The logarithmic derivative is obtained using this least
Adverb. partic.
squares representation.
The logarithmic derivative is obtained by using this least
Gerund phrase
squares representation.
Neglecting the dependence of n on Reynolds number, the
Adverb. partic.
results of figure 11 can be used to estimate n.
By neglecting the dependence of n on Reynolds number,
Gerund phrase
the results of figure 11 can be used to estimate n.
Substituting equation (34) instead of equation (14), the
Adverb. partic.
terms for the fluctuating modes can be rewritten.
By substituting equation (34) instead of equation (14), the
Gerund phrase
terms for the fluctuating modes can be rewritten.
Restoring by to these phrases adds very little to the above sentences. The participles in these sentences clearly
modify the verbs; thus their meaning is clear. But participles are, by definition, adjectives, so that adverbial
participles are not grammatical. Also there are methods of revising adverbial participles other than restoring their
by. In the following sentences, stronger constructions replace the participial phrases:
The logarithmic derivative is obtained from this least
Prep. phrase
squares representation.
With the dependence of n on Reynolds number neglected,
Prep. phrase
the results of figure 11 can be used to estimate n.
Substituting equation (34) instead of equation (15) allows
Gerund subject
the terms for the fluctuating modes to be rewritten.
Dangling participles
When a participle genuinely appears to modify the wrong noun, truly dangling and thus much more offensive:
Using a nonaligning pitot probe, the swirl cormponent
Dang. partic.
precludes exact measurement of total velocity.
When a nonaligning pitot tube is used, the swirl component
Better
precludes exact measurement of total velocity.
The shock is essentially normal near the body, producing
Dang. partic.
subsonic flow.
Near the body is an essentially normal shock producing
Better
subsonic flow.
Encouraged by these results, a new research effort was
Dang. partic.
begun.
Encouraged by these results, we began a new research
Better
effort.
Recommendations
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· When an introductory gerund or infinitive phrase is clearly adverbial, we consider its use idiomatic and therefore
we do not consider it dangling.
Although no writing authorities now claim that adverbial participles and nonidiomatic absolute participles are
becoming acceptable in technical writing, such participles are widely used and well understood. Forbidding their
use is perhaps like forbidding the tide to rise. These participial constructions are certainly not grammatical, but
they are rarely misunderstood.
· So long as an adverbial or absolute participle does not appear to modify the wrong noun, it is acceptable, but not
encouraged.
Chapter 2. Sentence Structure - English Grammar - Perfect English Language Speaking & Writing Learning
2.1. Sentence Structure
Effective writing involves far more than following rules of grammar. There is a craft to creating phrases,
sentences, and paragraphs that ensure communication. An editor, with the vantage point of a reader, can
contribute to this craft by looking for opportunities to improve sentence structure.
2.2. Subjects and Verbs
A sentence can make three types of statements:
· A subject does something (active verb)
Researchers write reports.
· A subject has something done to it (passive verb)
The reports are reviewed by editors.
· A subject is equal to something else (linking verb)
Reports are Langley's research product.
In all three types of sentences, the subject and verb are the most important elements. Since the subject and verb
are the most important elements in a sentence, improving their relationship, clarifying the subject, or making the
verb more vigorous will improve the sentence.
2.2.1. Clarify Subject
The importance of subject and verb may be an elementary idea, but the writer of the following sentences has
surely forgotten it:
An indication of probable asymmetric throat area reduction between the upper and lower throats of
this nozzle during reverse thrust operation is shown by the jet-lift coefficients presented in figure
28.
At NPR < 4, there is a large reduction in discharge coefficient due to reverse thrust operation,
indicating a decrease in the effective throat area for the nozzle.
The subject of a sentence should be expressed with clear, concrete words; and in technical documents, it usually
is. However, this clearly expressed topic of the sentence is often not the grammatical subject. In the first sample
sentence, indication is not the true subject; in the second sample, the subject and verb positions have been wasted
by an indirect construction, there is.
Effective Revenue Writing 2 (Linton 1962) suggests that the real subject of a sentence can be found by identifying
the real action in the sentence; the subject is then either receiving the action or preferably performing it. In the first
sample sentence, identify the action. From among the several words of action (indication, reduction, operation, is
shown, presented), indication seems most important. Two revisions come to mind when indicate becomes the
main verb:
Asymmetric throat area reduction between the upper and lower throats of this nozzle during
reverse thrust operation is probably indicated by the jet lift coefficients presented in figure 28.
The jet lift coefficients presented in figure 28 indicate a probable asyrnmetric throat area reduction
between the upper and lower throats of this nozzle during reverse thrust operation.
Which sounds best? The second revision, with an active verb close to its subject, is certainly easier to read. Out
of context, it is preferable. Context affects the choice of subject. For good transition from one sentence to
another, the subject of a sentence should relate to the previous sentence.
Now consider the second sample sentence, containing the indirect construction. The expletive there forces the true
action of the sentence, indicating, into a participial construction. Making indicate the main verb results in
At NPR < 4, a large reduction in discharge coefficient due to reverse thrust operation indicates a
decrease in the effective throat area for the nozzles.
Another indirect construction involves the pronoun it:
It appears that grain refining improved the toughness of
Indirect maraging steels.
Grain refining seemed to improve the toughness of
Better maraging steels.
It is obvious that a blackbody laser is feasible as a space
Indirect power system.
Obviously a blackbody laser is feasible as a space power
Better system.
As with any valid grammatical construction, indirect constructions sometimes serve a function, but many
grammar and writing books criticize them as being wordy (see section 2.4.1) and unnecessary. Rowland (1962)
states that "expletives serve only to mark time until the true grammatical subject appears." In Tichy and
Fourdrinier's (1988) opinion, as well as in Rowland's, indirect constructions can be ambiguous. Such idioms as
"it is known" or "it is believed" indicate general knowledge or belief:
It is believed that this is a nozzle-aspect-ratio effect.
In most technical writing, these constructions refer to the author's belief or knowledge. Perhaps a personal
pronoun is appropriate (see section 1.3.2):
We believe that this back pressure increase is a nozzle-aspect-ratio effect.
Note the change in the subordinate clause of this sentence. Demonstrative pronouns (this, these, that, or those
used as nouns) with "broad reference" (Ebbitt and Ebbitt 1982) can be undesirable and ungrammatical when their
antecedent is not clear (see section 1.3.1):
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Mass flow rate increased in the cove. This resulted in
Poor
increased cove gas temperature.
The increasing mass flow rate in the cove increased cove
Better
gas temperature.
Please do not insert stock abstract words such as result, effect, or apparatus after every demonstrative pronoun.
Remember that the subject of a sentence (or clause) should be clear and concrete and should relate to previous
ideas.
2.2.2. Make Verbs Vigorous
The only words capable of expressing action are verbs and their derivatives. Invigorating verbs will make writing
more concise and easier to read. In the following phrases, the action of the verb reduce is progressively
deemphasized:
Active voice If we reduce drag, . . .
Passive voice If drag is reduced, ...
Verbal With reduced drag, ...
Verb-derived noun With reduction of drag, . . .
Weak verbs
One of the most common causes of weak verbs has already been discussed; when the real verb of a sentence
becomes the subject, a weaker verb must be substituted:
A comparison of lift coefficients for the two configurations
Poor
is presented in table II.
Lift coefficients for the two configurations are compared in
Better
table II.
The agreement between calculated and experimental heating
Poor rates was within 30 percent.
Calculated and experimental heating rates agreed to within
Better 30 percent.
Asymmetric throat area reduction between the upper and
Poor lower throats occurred during reverse thrust operation.
Throat area decreased asymmetrically between the upper
Better and lower throats during reverse thrust operation.
Another method of weakening verbs is to hedge with such words as might, may, seem to, appear to, or tend to.
Hedges not only weaken the verb, as they are meant to, but also imply indecision on the part of the author. They
should not be overused (see section 2.4.1).
Active versus passive voice
As discussed in section 1.4.3, writing authorities overwhelmingly prefer active voice to passive voice. However,
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Tichy and Fourdrinier (1988) list five situations when passive voice is appropriate:
· When the actor is unimportant, not known, or not to be mentioned
· When the receiver of the action should be emphasized
· When the sentence is abrupt in active voice
· When variety is needed in an active voice passage
· When a weak imperative is needed
Although the first two items justify much of the passive voice in technical documents, the converse of the fourth
item must also be considered. In our passive voice reports, an occasional active voice sentence is needed for
variety. (Tichy and Fourdrinier 1988 also discuss the importance of sentence variety to good style.) Thus editors
should watch for sentences that could appropriately be revised to active voice:
The dependence of n on Mach number was reduced at
Passive
higher Reynolds numbers.
The dependence of n on Mach number decreased at higher
Active
Reynolds numbers.
Increasing Reynolds number reduced the dependence of n
Or
on Mach number.
The reduction in discharge coefficient is probably caused by
Passive
an increase in back pressure.
An increase in back pressure probably causes the reduction
Active
in discharge coefficient.
Pressures and cold-wall heating rates, normalized with
Passive
respect to wing surface conditions, are shown in figures 2
and 3.
Figures 2 and 3 show pressures and cold-wall heating rates,
Active
normalized with respect to wing surface conditions.
The active version of the last example ascribes a human ability (to show) to an inanimate object (figure), a
rhetorical device commonly called personification. Rowland (1962) states, "Personification, if not overdone, is
an effective means of conferring vigor and emphasis. . . and affords relief from excessive use of passive voice."
Bernstein (1981) agrees, but both caution against ludicrous attributions (called pathetic fallacy); for example,
Nonessential loads can take advantage of voltage regulation,
Path. fallacy
but essential loads cannot.
For nonessential loads, designers can take advantage of
Better
voltage regulation, but for essential loads, they cannot.
Linking verbs also can sometimes be converted to active voice:
The velocity and density sensitivities are both dependent on
Linking verb
Mach number.
The velocity and density sensitivities both depend on Mach
Active
number.
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Verbals
Active writing does not require active voice, since there are other types of active constructions (Linton 1962):
Prepositional phrase: methods for reduction of...
Gerund phrase: methods for reducing...
Infinitive phrase: methods to reduce...
The emphasis on the action increases from the prepositional to the gerund phrase and from the gerund to the
infinitive phrase.
2.2.3. Improve Subject-Verb Relationship
The subject and verb should be the most important elements of a sentence. Too many modifiers, particularly
between the subject and verb, can over-power these elements. If modifiers are more interesting and active than the
sentence itself (subject-verb-object), the action of at least some modifiers should be transferred either to the main
verb or to a new sentence or independent clause:
The test medium is the combustion products of methane and
Poor
air, which are produced in a high-pressure combustor,
expanded through an axisymmetric contoured nozzle, and
diffused and pumped from the test section to the atmosphere
through an annular air ejector.
The test medium, the combustion products of methane and
Better
air, is produced in a high-pressure combustor, expanded
through an axisymmetric contoured nozzle, and diffused
and pumped from the test section to the atmosphere through
an annular air ejector.
The test medium is the combustion products of methane and
Or
air. These gases are burned in a high-pressure combustor,
and the combustion products are expanded through an
axisymmetric contoured nozzle and diffused and pumped
from the test section to the atmosphere through an annular
air ejector.
When placed between the subject and verb, too many modifiers can ruin the continuity of the sentence. A reader
may not be able to recall the subject by the time the verb comes along. Adverbial modifiers can often be moved,
but adjective phrases and clauses present a special problem because they cannot wander far from the noun that
they modify:
Pressures that were sensed at discrete locations such as in the cavity just behind the seal, at the
bulkhead, and at the base of the elevon and ramp are also given.
When a long adjective phrase or clause intrudes between the subject and verb, four choices for revision are
available:
· Shorten the intervening adjective:
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Pressures sensed at discrete locations, such as at the bulkhead, are also given.
· Invert the subject and verb:
Also given are pressures that were sensed at discrete locations such as in the cavity just behind the
seal, at the bulkhead, and at the base of the elevon and ramp.
Inverting a sentence drastically changes emphasis and often sounds artificial.
· Place the verb between the subject and the adjective if the verb phrase is short and modification is clear:
Pressures are also given which were sensed at discrete locations such as in the cavity just behind
the seal, at the bulkhead, and at the base of the elevon and the ramp.
We realize that it is ungrammatical to place a verb between a relative clause and its antecedent. Effective Revenue
Writing 2 (Linton 1962) condones this infraction as long as modification is clear.
· Change the adjective clause to an adverbial phrase
Pressures are also given for discrete locations such as in the cavity just behind the seal, at the
bulkhead, and at the base of the elevon and the ramp.
Changing adjectives to adverbs often changes meaning.
2.3. Parallelism
Parallelism is an important and often neglected syntactic consideration. To quote Tichy and Fourdrinier (1988),
A major device for sentence emphasis is parallel construction. Equal thoughts demand expression
in the same grammatical form. Repetition of structure within a sentence is a most effective device
for making the long sentence easy to read, and repetition of structure in two or more sentences
connects them. An understanding of parallelism is therefore essential for emphasis and coherence.
When should sentence elements be parallel and how do we make them so? When two or more ideas are logically
equal, they should be made parallel by writing them in the same grammatical structure. Grammatically, words are
equal (parallel) to words, phrases to phrases, subordinate clauses to subordinate clauses, and independent clauses
to independent clauses. Parallel grammatical elements are also called "coordinate."
Logic dictates the use of parallelism, or coordination. For example, the two coordinate clauses in the following
sentence are not logically equal:
The compressor may be operated in the compression mode and then the flow is expelled from the
anechoic room to the test duct.
This sentence calls for subordination, not coordination:
When the compressor operates in the compression mode, the flow is expelled from the anechoic
room to the test duct.
Except for coordinate clauses, such as the example above, sentence elements that are not logically parallel are
rarely found in parallel construction. However, logically parallel ideas are often not written in grammatically
parallel structure.
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parallel structure.
2.3.1. Connectives Requiring Parallelism
Effective Revenue Writing 2 (Linton 1962) lists four types of connectives requiring parallelism coordinate
conjunctions (and, or, but), correlative conjunctions (either . . . or, both . . . and, not only . . . but also),
conjunctive adverbs (therefore, otherwise, however), and the semicolon used to connect independent clauses.
Coordinate conjunctions probably provide the most opportunities to use parallelism. As discussed in section
1.8.1, they join words, phrases, and clauses of equal grammatical rank. Coordinate clauses joined by a
coordinate conjunction should be logically equal. Similarity in grammatical structure, if possible, is also a good
idea. For example, the voice of the verb might be kept the same:
The mixing noise is the dominant component of the
Acceptable
spectrum, but the background noise peaks at a high
frequency.
The mixing noise dominates the spectrum, but the
Better
background noise peaks at a high frequency.
Correlative conjunctions demand strict parallelism: Both elements of the correlative must be followed by the same
part of speech (see section 1.8.1).
Independent clauses joined by conjunctive adverbs or simply by a semicolon should also be logically coordinate;
however, grammatical parallelism is an option to be used for emphasis or contrast:
In the compression mode, the duct serves as an eductor; in the exhaust mode, it serves as an inductor.
2.3.2. Itemization
As mentioned earlier, repetition of structure is effective in making long sentences easy to read. Itemization is
another important device for making a sentence containing several long parallel elements easy, perhaps possible,
to read. Itemization can also be used to emphasize the individual parallel elements.
Itemization is a special form of parallelism. The introductory phrase or clause leading into the list should read
logically into each item:
The test indicated
1. That continuous thermal exposure degraded the strength of the composite material.
2. That cyclic thermal exposure did not degrade the strength of the composite material.
In the above example, the common element, that would usually be included in the introductory clause: "The test
indicated that."
In an itemization, all items must be the same grammatical construction, for example, all prepositional phrases, all
noun phrases, or all complete sentences:
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Continuous cyclic exposure resulted in
Poor
1. The matrix diffusing to the reaction layer
2. Degradation of the strength of the composite
material
Continuous cyclic exposure resulted in
Better
1. Diffusion of the matrix to the reaction layer
2. Degradation of the strength of the composite
material
The investigation was conducted
Poor
1. To determine mechanisms causing strength
degradation
2. Because the rate of degradation varied widely
depending on the composite matrix
The investigation was conducted
Better
1. To determine mechanisms causing strength
degradation
2. To explain the wide variation in degradation rate for
various composite matrixes
2.4. Brevity and Conciseness
Technical writing should be concise, free of redundancy and unnecessary detail. Minimizing the number of words
to achieve brevity does not necessarily result in conciseness and may destroy the emphasis, the pace, and perhaps
the meaning of a passage. However, wordiness seems to be a common fault of technical writing, and editors
should delete unnecessary or redundant words.
2.4.1. Wordiness
Many reference books contain sections containing lists of wordy, redundant, or trite expressions (for example,
Skillin et al. 1974, p. 407ff; and Rowland 1962, chapter XIV). We suggest that writers and editors occasionally
peruse such lists in order to remain sensitive to unnecessary wordiness. Tichy and Fourdrinier (1988) classify
seven types of common wordiness and list numerous examples of each:
· Tautology, the unnecessary repetition of an idea
ac current Omit current
20 sec in duration Omit in duration
close proximity Omit close
in the range of 1to 10 Replace in the range of with from
· Dilute verbs (see section 2.2.2)
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are found to be in agreement Use agree
analyses were made Use analyze
make adjustments to Use adjust
give consideration to Use consider
take measurements of Use measure
· Hiccups, superfluous prepositions and adverbs
of from Omit of
call for Use demand
enter into Omit into
in between Omit in
inside of Omit of
go on with Use continue
· Roundabout constructions
There are three distinct flow characteristics in these
Poor
photographs.
These photographs show three distinct flow characteristics.
Better
It might be expected that there would be some flow
Poor
separation.
Some flow separation might be expected.
Better
It appears that the flow field over the nozzles is complex.
Poor
The flow field over the nozzles appears to be complex.
Better
It was shown in reference 1 that...
Poor
Reference 1 showed that...
Better
Hathwell (ref. 1) showed that...
Or
· Hedging and intensifying
Lift tends to increase with angle of attack.
Hedge
Lift increases with angle of attack.
Better
This alloy appears to be a candidate material for...
Hedge
This alloy is a candidate material for...
Better
· Unnecessary intensifiers
more dominant
quite impossible
very unique
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· Pointless words and phrases
It is interesting to note that
It might be stated that
In the case when
· False elegance
a majority of Use most (unless over 50% is meant)
due to the fact that Use because
in close proximity Use near
with the exception of Use except
2.4.2. Shortening Text
Occasionally, a passage may be wordy, to the point of being difficult to read, or it may exceed a limiting number
of words (for example, NASA limits abstracts to 200 words). Linton (1962) suggests five ways to economize:
· Reduce syntactic weight by subordinating sentences, changing subordinate clauses to phrases, and reducing
phrases to adverbs and adjectives:
Any ash that was not carried into the stratosphere moved toward the northeast into a bank of
mammatus clouds. Mammatus clouds have downward accelerations and upward velocities. They
thus allow the larger particles to drift downward.
Any ash not carried into the stratosphere moved northeasterly into a bank of mammatus clouds.
The downward acceleration and upward velocity of these clouds allowed the larger particles to
drift downward.
· Avoid redundant and roundabout phrases (see section 2.4.1).
· Avoid passive voice (see section 2.2.2).
· Prefer active verbs to verbs expressing state of being, that is, linking verbs and such words as appear and seem.
· Combine ideas of several sentences into one. Of course, avoid long, confusing sentences; but many short,
simple sentences waste words:
There were three distinct flow characteristics. Ahead of the wing, a bow wave of water droplets
was observed. On the wing surface, a continuous water film formed. Between 16.7 and 41.7
percent of the chord, the film broke down into discrete runoff streams.
The three observed flow characteristics were a bow wave of water droplets ahead of the wing, a
continuous water film on the wing surface, and discrete runoff streams beginning at 16.7 to 41.7
percent of the chord.
2.4.3. Shortening Titles
Conciseness is especially important in titles; a short title improves the appearance of the cover and a precise title
indicates what readers can expect to find inside the cover. Brevity and preciseness must be balanced so that in a
minimum number of words, the title is correct (it presents the topic of the paper), complete (it expresses the limits
of the paper), comprehensible (potential readers will understand it), and concise (it is as efficient as possible).
A title which passes this evaluation (from Rathbone 1985) may be anything but brief. Rathbone also suggests that
titles be shortened by deleting familiar phrases which concern reporting or information gathering. Such phrases as
An Investigation of ...
An Analysis of ...
Conference on ...
can often simply be dropped without changing the meaning of the title. Unnecessary articles should also be
deleted. Often a title becomes lengthy and awkward because several prepositional phrases have been added to
qualify it. Several approaches can be taken. A prepositional phrase can be changed to a unit modifier:
Analysis of Hydroelastic Vibrations of Shells Partially
Title
Filled With a Liquid Using a Series Representation of the
Liquid
Hydroelastic Vibration Analysis of Partially Liquid-Filled
Revision
Shells Using a Series Representation of the Liquid
Note: In this title, analysis cannot be deleted because using modifies it.
· Care must be taken to keep the title comprehensible. A string of unit modifiers can be as awkward as a series of
prepositional phrases, and far more ambiguous.
Another approach for reducing the number of prepositions is to make subtitles:
Low-Speed Wind-Tunnel Investigation of Flight Spoilers as
Title
Trailing-Vortex-Alleviation Devices on a Medium-Range
Wide-Body Tri-Jet Airplane Model
Flight Spoilers for Trailing Vortex Alleviation - Low-Speed
Revision
Wind-Tunnel Results for a Medium-Range Wide-Body Tri-
Jet Airplane Model
Note: This revision not only removes a prepositional phrase, but also emphasizes the theme of the
paper.
A title can be livened up and prepositions removed by changing verb-derived nouns to verbals, for example,
Alleviation of Trailing Vortexes by Use of Flight Spoilers
Title
Alleviating Trailing Vortexes by Deflecting Flight Spoilers
Revision
Of course, titles must not be shortened indiscriminately. Keep in mind the goal of maximum information in a
minimum of words. In the previous example, use was not changed to deflect with brevity in mind. However, the
word deflect adds to the spirit of conciseness because it means more. Consider replacing or clarifying words with
vague meaning such as method,system, facility, use, or approach. The following example illustrates this point:
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An Instrumentation System for Helicopter Blade Flight
Title
Research Measurements
A Rotor-Mounted Digital Instrumentation System for
Revision
Helicopter Blade Flight Research
The revision is two words longer, but it seems more concise because it says so much more with only two more
words.
2.5. Comparisons
Comparisons are of major importance in technical writing; experimental results are compared with predictions,
results at standard or control conditions with results at test conditions, full-scale data with model-scale data,
characteristics of one configuration with those of another. Such comparisons can be complicated and therefore
should be expressed as simple, straight-forward constructions.
The most frequent problem with comparison is ambiguity concerning the items being compared:
Comparison between pressures on the nozzle and boattail
Poor
and the tail boom indicates...
Comparison of pressures on the nozzle and boattail with
Better
those on the tail boom indicates...
The goal of the program was to obtain tougher martensitic
Poor
steel alloys.
The goal of the program was to obtain tougher martensitic
Better
steel alloys than are commercially available.
2.5.1. Comparison of Adjectives and Adverbs
Adjectives and adverbs change form to indicate degree of comparison (IRS 1962):
· Positive degree merely indicates existence of a quality.
· Comparative degree indicates a quality existing to a greater or lesser degree in one thing than in another.
· Superlative degree indicates a quality existing to the greatest or least degree in a group of things.
Comparative degree is formed by adding the suffix er or adding more or less before the modifier. Superlative
degree is formed by adding the suffix est or adding most or least before the modifier.
Most adjectives with three or more syllables and almost all adverbs are compared by adding more and most (or
less and least). In addition, some modifiers, for example, good, have irregular comparisons; the words
themselves change:
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Positive Comparitive Superlative
high higher highest
dependable more dependable most dependable
carefully less carefully least carefully
good better best
far farther, further farthest, furthest
· The comparative degree is used to compare two persons or things or to compare a person or thing with a class:
Pressures were higher on the left nozzle than on the right nozzle.
The values from the second test varied more than those from the first test.
Pressures were higher at orifice 7 than at the other 47 orifices.
Note the use of other in the last example; either other or else is required when a person or thing is compared with
a class in comparative degree.
· The superlative degree is used to compare more than two persons or things. The word all (not any) is used with
superlative degree for comparison with a class.
Of four nozzle configurations, the dry power nozzle experienced the highest pressures.
The values from the eighth test varied most.
Pressures at orifice 7 were highest of those at all 48 orifices.
2.5.2. Ambiguous Comparisons
Tichy and Fourdrinier (1988) discuss several types of errors which obscure meaning in comparisons: incomplete
comparisons and omission of standard are often encountered in technical writing.
Incomplete comparisons
Unless all necessary words are included, many comparison sentences have two meanings:
The astronaut could hear her companion better than the
Ambig.
control operator.
The astronaut could hear her companion better than the
Either
control operator could.
The astronaut could hear her companion better than she
Or
could hear the control operator.
Demonstrative pronouns are often used to complete comparisons (see section 1.3.4):
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The pressures on the left dry-power nozzle are lower than
Poor
the right afterburning-power nozzle.
The pressures on the left dry-power nozzle are lower than
Better
those on the right afterburning-power nozzle.
The pressures are lower on the left dry-power nozzle than
Or
on the right afterburning-power nozzle.
If the antecedent of the demonstrative pronoun is obscure, reword the sentence or repeat the subject of
comparison.
The axial force on the left dry-power nozzle in the presence
Poor
of a right afterburning-power nozzle was lower than that in
the presence of a right dry-power nozzle.
The axial force on the left dry-power nozzle was lower in
Better
the presence of a right afterburning-power nozzle than in the
presence of a right dry-power nozzle.
Omission of standard of comparison
Unless the standard of comparison is clear, comparisons are meaningless:
At the higher angles of attack, flow separation is extensive.
Poor
At high angles of attack, flow separation is extensive.
Better
Higher strength martensitic steels are attractive candidate
Poor
cryogenic materials.
Martensitic steels, which are stronger than ferritic steels, are
Better
attractive candidate cryogenic materials.
2.5.3. Comparison Constructions
So far in this section, only comparison constructions involving than have been discussed. Several other
constructions may be used, or misused, to express comparisons.
Compare with
The verb compare takes either to or with, depending on meaning. Bernstein (1981), explains the use of with quite
clearly "When the purpose is to place one thing side by side with another, to examine their differences or their
similarities, use with." In technical writing, do comparisons ever have any other purpose?
The participle compared with is often used (sometimes in a dangling construction) when another construction
would be better:
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The grain-refined material was much tougher compared
Poor
with the control material.
The grain-refined material was much tougher than the
Better
control material.
The grain-refining heat treatment increased toughness by 10
Poor
percent compared with the control material.
The grain-refining heat treatment increased toughness of the
Better
control material by 10 percent.
The configuration with fuselage incidence experienced an
Poor
increase in drag coefficient of 2 percent compared with the
baseline configuration.
The configuration with fuselage incidence experienced an
Better
increase in drag coefficient of 2 percent over that of the
baseline configuration.
As... as
The correlative construction as ... as is an excellent method of indicating similarity, or dissimilarity:
The ferritic steels are not as tough at cryogenic temperature as at room temperature.
The second as should not be omitted when a comparative degree rmodifier intervenes:
After grain refinement, the steel is as hard if not harder than
Poor
hefore.
After grain refinement, the steel is as hard as, if not harder
Better
than, before.
After grain refinement, the steel is as hard as before, if not
Or
harder.
Different
The adjective different is often used superfluously:
Figure 16 presents data from two
Poor different wind-tunnel runs.
Figure 16 presents data from two wind-
Better tunnel runs.
Note that different should not be indiscriminately deleted. The above sentence could have meant
Figure 16 presents data from two wind-tunnel runs at different conditions.
When possible, change the predicate adjective different to the verb differ, a more vigorous construction (see
section 2.2.2):
The trends on the lower surface are different from those on the upper surface.
The trends on the lower surface differ from those on the upper surface.
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· Different takes the preposition from:
The measurements on the lower surface showed a different
Poor
trend than those on the upper surface.
The measurements on the lower surface showed a different
Better
trend from those on the upper surface.
Bernstein (1981) explains the rare occasions when different than is appropriate to avoid the elaborate construction
from that which:
In error analysis, standard deviation may be calculated with a different equation than in statistical
analysis.
Just as demonstrative pronouns are sometimes needed to cornplete a comparison (section 2.5.2), they are
sometimes needed with different:
The interpretation of "standard deviation" in error analysis
Poor
is different from statistical analysis.
The interpretation of "standard deviation" in error analysis
Better
is different from that in statistical analysis.
The..., the
An effective method of comparison is the idiomatic correlative construction involving the ..., the:
The lower the temperature, the more brittle the steel becomes.
2.6. Emphasis
The subject of sentence emphasis is often neglected by authors and editors. Many writers must resort to
underlining (or italicizing) to emphasize an idea because they do not understand methods of emphasis (see section
3.9.1). Editors who do not pay attention to emphasis cannot assist these authors and, worse yet, may overlook
the effect that editorial revisions have on sentence emphasis.
"Any sentence markedly different from the preceding sentences receives stress-a short sentence after several long
ones; a periodic sentence after loose sentences; a simple sentence after a series of complex, compound, or
compound-complex sentences" (Tichy and Fourdrinier 1988). Be sure that a contrasting sentence contains an
important idea.
2.6.1. Emphasizing With Sentence Structure
The above quote from Tichy and Fourdrinier illustrates a most effective method of emphasis: parallelism. As
discussed in sections 1.8.1 and 2.3, parallelism is grammatically required at times. It can also be used to
Chapter 2. Sentence Structure - English Grammar - Perfect English Language Speaking & Writing Learning
emphasize the likeness or contrast between items. In parallel constructions, emphasis on the individual parallel
items can be increased by repeating articles, prepositions, or introductory words:
Pressure distributions were obtained on the wing, elevon, and cove walls.
Pressure distributions were obtained on the wing, on the elevon, and on the cove walls.
The study indicated that thermal cycling caused matrix cracking and fatigue cycling caused no
damage.
The study indicated that thermal cycling caused matrix cracking and that fatigue cycling caused no
damage.
Of course, the most emphatic way to list parallel elements is to itemize them:
The study indicated that
1. Thermal cycling caused matrix cracking.
2. Fatigue cycling caused no damage.
Positions of emphasis in a sentence are the beginning and the end. Therefore, if a modifying phrase is moved to
the beginning of a sentence, that phrase receives emphasis:
Cove cold-wall heating rates at zero leakage decreased from 2 percent of the wing heating rate.
At zero leakage, cove cold-wall heating rates decreased from 2 percent of the wing heating rate.
Emphasis can be added to internal sentence elements by moving them to an unusual position:
After each session of noise, the subjects rated overall noisiness, among other things.
After each session of noise, the subjects rated, among other things, the overall noisiness.
Be careful not to misplace the modifier:
After each session of noise, the subjects, among other things, rated the overall noisiness.
Rhetorical connectives, such as however, therefore, hence, and thus, can serve to emphasize elements of a
sentence. Placing such adverbs within a sentence emphasizes the words immediately preceding them (Linton
1962):
However, isothermal exposure did increase ductility in the matrix material.
Isothermal exposure, however, did increase ductility in the matrix material.
Isothermal exposure did, however, increase ductility in the matrix material.
Commas around such adverbs may be omitted to decrease emphasis, and of course commas would never be used
around these adverbs when they are restrictive (Rowland 1962):
Isothermal exposure thus increased ductility in the matrix material.
2.6.2. Emphasizing With Punctuation
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As indicated above, commas around rhetorical adverbs and other interrupting elements (section 3.5.2) increase
emphasis on the enclosed element. A comma between coordinate adjectives adds emphasis to the adjectives as
separate modifiers:
The delta function has a long, controversial history
Replacing tire comma with and further increases this emphasis:
The delta function has a long and controversial history
Note however that only coordinate adjectives can be punctuated this way (see section 3.5.1).
Other marks of punctuation affect emphasis. Using a colon to introduce a list tends to emphasize the list:
The scatterometer is separated into a gimbal, a transmitter-receiver assembly, and rack-mounted
electronics.
The scatterometer is separated into three assemblies: a gimbal, a transmitter-receiver assembly, and
rack-mounted electronics.
The dash, when used carefully, is an emphatic mark-it can be used to emphasize interrupting elements,
nonrestrictive modifiers, and explanatory phrases and clauses (see section 3.6):
Auxiliary meteorological data used herein -- such as vorticity -- have been computed from NMC isobaric height
fields.
The one-sided spectrum -- engineers call it simply "spectrum" -- is the output of most spectral analyzers.
Other random processes have average properties that vary appreciably with time -- for example, the load demand
on an electric power generating system.
