Parentheses, Brackets, and Braces

What’s the difference?

Bonnie Mills, Writing for
5-minute read
Episode #233

bracketsToday Bonnie Trenga will help us talk about three punctuation marks: one you undoubtedly know how to use, another you possibly misuse, and yet another you’ve likely never used. If you’ve ever wondered when to favor parentheses over square brackets and when to stick in a pair of curly braces, listen on.


You’re probably well versed in how to use those sideways eyebrow thingies, better known as parentheses. First, remember that a pair of them is called “parentheses,” whereas a single one is a “parenthesis.” You may want to review episode 222 in which we compared parentheses to dashes and commas. For now, let’s just say that parentheses mainly enclose information that is not vital to a sentence. No matter what you put within parentheses, your sentence must still make sense if you delete them and everything inside. Note that you are allowed to put both partial sentences and complete sentences within parentheses. But no more than a whole paragraph, please, requests authority Brian Garner (1).

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Before we move on, we need to address one issue: how to use terminal punctuation marks with parentheses. If your sentence starts with an opening parenthesis, then what’s inside your parentheses is a complete sentence. You must therefore ensure that the terminal punctuation mark, such as a period, question mark, or exclamation point, goes inside the closing parenthesis: “(I knew he wouldn’t want to do that.)” If what’s within the parentheses is only a partial sentence, put the terminal punctuation outside instead: “I moved to America when I was 10 (in 1980).”

For the most part, these two rules seem fairly easy to understand—complete sentence: terminal punctuation inside; partial sentence: terminal punctuation outside. However, when you have a sentence that contains another complete sentence within parentheses, the punctuation could become confusing. Let’s say you want to add the complete sentence “I can’t believe it!” inside parentheses within another complete sentence. In this case, the exclamation point would go inside the closing parenthesis and then a period would go outside: “I ate the whole box of donuts (I can’t believe it!).”

That works, but I often recommend making the sentence inside parentheses a complete sentence on its own that follows the first sentence. Make sure you have a reason for putting it in parentheses.

Next: Square Brackets


About the Author

Bonnie Mills, Writing for Grammar Girl

Bonnie Mills has been a copyeditor since 1996.