10. English Language Punctuation - Parentheses Parentheses may be used to enclose nonrestrictive or interrupting elements. Commas or dashes may also be used for this purpose. Parentheses are most appropriate to enclose a nonrestrictive element that is only loosely connected to the sentence and could be left out without damaging the sentence. Do not insert a parenthetical element with no relation whatever to the rest of the sentence. The following example is taken from Fowler (1944): In writing this straightforward and workmanlike biography of his grandfather (the book was finished before the war and delayed in publication) Mr. Walter Jerrold has aimed at doing justice to Douglas Jerrold .... The parenthetical idea has no bearing on the sentence! Parentheses enclose numbers in an enumeration within a sentence: The scatterometer is separated into (a) a gimbal, (b) a transmitter-receiver assembly, and (c) rackmounted electronics. When the enumerated list is displayed, a period following the number is sufficient to set it off (Skillin et al. 1974; and Chicago Press 1982): The scatterometer is separated into 1. English Language Punctuation - 2. English Language Punctuation - A gimbal A transmitter-receiver assembly Rack-mounted electronics Ebbitt and Ebbitt (1982) neatly explain use of parentheses with other punctuation marks as follows: When a complete sentence in parentheses comes within a sentence (notice the punctuation of this one), it needs neither a capital letter nor a period. Commas and other marks of punctuation in the main sentence always follow the parenthesis (as here and in the preceding sentence). (A sentence in parentheses, like this one, that does not stand within another sentence has the end punctuation before the closing parenthesis.) Punctuation (for example, question marks, quotation marks) of the ideas within parentheses remains within parentheses, while punctuation of the main sentence remains outside, almost always after the closing parenthesis rather than before an opening parenthesis. A comma precedes an open parenthesis if the parenthetical matter clearly limits the word following it (Skillin et al. 1974): Despite these differences, (digital) image-gathering systems can be compared with optical imaging systems.
