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Which of the following two forms is correct? (And if there's no agreement about that, which one is more common?)

a (optional) parameter
an (optional) parameter

The problem is that the choice between "a" and "an" is based on the spoken form of the phrase ("does the next word start with a vowel sound?"), but there is no spoken equivalent to parentheses.

I.e. I can say either:

a parameter


an optional parameter

But I can't pronounce parentheses.

marked as duplicate by Armen Ծիրունյան, svick, Andrew Leach Oct 9 '14 at 15:58

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  • The correct form is "an (optional) parameter." Otherwise, you are assuming that your reader is going to ignore everything inside the parentheses. That isn't what parentheses are for. If you want to include material that your readers don't have to read, put it in a footnote. – Peter Shor Oct 9 '14 at 15:20
  • The question is: How would you speak it aloud? Whether you would pronounce the parenthetical adjective or not will determine what the next word is. And it's the next spoken word that determines. So say it out loud. That is the rule for a/an: Say it out loud. – John Lawler Oct 9 '14 at 15:21
  • You could of course resort to "a(n) (optional) parameter", although I agree that it is not pretty. – painfulenglish Oct 9 '14 at 15:26
  • @JohnLawler That's the problem, I don't think I can say it out loud without losing (some of) the meaning. – svick Oct 9 '14 at 15:29
  • 1
    Parentheses are inaudible. You can do things in writing you cant do in talking, and vice versa. Mostly vice versa, in fact. But even if you wanna use an effect only available in written language like optional words, you still hafta deal with the effects only available in spoken language, like a versus an. You gotta say it aloud; if that loses information, too bad. Avoid saying it and avoid using an indefinite article, then; or give up on preserving all the information in every medium. Bandwidth is not infinite. – John Lawler Oct 9 '14 at 15:48

"a parameter (which is optional)"

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