Parentheses may be used to surround words, phrases or even whole sentences that are relatively unimportant to the main text. But they can distract the reader from your main point. Think about deleting the unimportant text. If a sentence must contain incidental information, setting off the information with a pair of commas or a pair of dashes may be more effective. Also try placing the extra information in a separate sentence - with no parentheses.

Parenthesis marks always come in twos, one opening and one closing ( ). Don't use one without the other, including if they're used in numbered or alphabetized lists.

Place a period outside a closing parenthesis if the material inside is not a sentence (such as this fragment). If a parenthetical sentence (here is one example) is part of a sentence, don't capitalize the first word or end the parenthetical sentence with a period. But if the parenthetical sentence ends with a question mark or exclamation point, put a period after the closing parenthesis (here's another example!). If the material in the parentheses is an independent sentence, capitalize the first word and place the period before the closing parenthesis. (Here is an example.)