General Rules:

  • Parentheses are generally used to show incidental information.

  • Parenthetical asides are acceptable as long as they're not too lengthy or used excessively.

  • Whether you set off information with commas, em dashes or parentheses will depend on which provides the best flow in the sentence.


Parenthetical Fragments


Rule: The period goes outside the closing parenthesis when the parenthetical information is not a complete sentence.

  • Example: The sun is shining (which is better than another rainy day).


Stand-Alone Complete Sentences


Rule: The period goes inside the closing parenthesis when the parenthetical information is an independent sentence.

  • Example: The laundry is almost all washed. (There were eight loads when she started washing it.)


Dependent Complete Sentences


Rule: Omit end punctuation and normal sentence capitalization when an independent sentence enclosed in parentheses is dependent on the rest of the sentence it falls within.

  • Example: The drive is shorter (it felt much longer on the return trip) than expected.