Back to Basics: How to Use Parentheses

Parentheses have all kinds of different functions: In academic papers, you’ll see them used for citations and maybe even in a few mathematical equations. In more casual writing, they’re used to insert extra information or relevant commentary. They’re handy if you want to toss in a humorous aside or demonstrate your point with some examples.

It might sound like parentheses are complicated, but their role can actually be broken down into just a few main functions. Here’s a complete guide to the most common uses for parentheses with some warnings about the most common MISTAKES!

Parentheses Are Interrupters

We’ll get into the specific roles of parentheses in just a second, but the overall takeaway should be that parentheses are almost always interrupters.

Parentheses might contain full sentences, short phrases, or even just a word or two, but whatever’s inside should not be essential to the meaning of your writing. By putting something in parentheses, you’re indicating that the information—albeit relevant and maybe even helpful—is not important.

Parentheses act like a hiding place for what’s inside, so be careful about what you put in there. Don’t get me wrong: they’re super handy in many cases! Just make sure you understand the effect that parentheses have on your writing so you don’t accidentally hide something that’s super important.

4 Uses for Parentheses

Additions and Interruptions

Parentheses can be used to set off additional information in your writing. This extra information might be an aside, some examples, a citation, or anything else that is NOT essential to the central meaning of your writing.

There are a few different interrupters in the English language: parentheses, commas, and dashes. Of the three, parentheses indicate the strongest separation. Check out these examples to see what I mean:

Snow White worked hard and was cheerful, though the Evil Queen treated her poorly.

Snow White worked hard and was cheerful—though the Evil Queen treated her poorly.

Snow White worked hard and was cheerful (though the Evil Queen treated her poorly).

The first sentence reads smoothly, with just a short pause between “cheerful” and “though.” The dash makes you pause a little longer but still balances both sides of the sentence pretty evenly (neither side of the sentence seems more important than the other).

With the parentheses, the bit about the Evil Queen seems more like an aside than part of the actual sentence, and it puts emphasis on the first statement (the one that’s not in parentheses). As a reader, I expect to hear more about Snow White—not the Evil Queen—in the coming story because Snow White and her cheerful demeanor are emphasized as the main point of the sentence.

You can put anything from a single word to several full sentences inside parentheses. Here are some of the most common additions that are usually enclosed in parentheses:

• examples: “I picked up some basic groceries (bread, milk, eggs, etc.) because I wasn’t sure what my friend would want to eat.”
• definitions of unfamiliar or unusual words: “It’s polite to give a salutation (a gesture of greeting) when someone comes into the room.”
• translations of words from other languages: “Damas (“ladies”) was printed on the bathroom door.”
• the introduction of abbreviations: “The Oxford English Dictionary (OED) defines parentheses as marks that enclose nonessential words, phrases, and even whole sentences.”
• directions to help readers find further information: “The findings of this study were significant (see Figure 3).”
• numerical equivalents: “Make sure to bring two (2) pens to class.”

In The Copyeditor’s Handbook, Amy Einsohn reminds us that parentheses are not for critical information. She said that parentheses “set off an interrupter that has a relatively unimportant point, trivial exception, or brief list of examples.”

In-Text Citations

If you’re writing an academic paper, you need to include citations. Citing your sources is an essential step in establishing credibility and maintaining integrity. If you reference another person’s work, you need to give them credit! Many style guides recommend using parenthetical citations in the body of your paper with a list of full citations at the end.

In your list of citations at the end of your paper, you’ll include a lot of information about the sources you’re citing. But in the paper itself, you’ll just include a brief citation; this citation may include the author’s last name and publication date.

For example, the APA style guide requires citations like this:

Recent studies indicate that this may be true (Smith, 2005).

The exact format of your in-text citation (and what information you should include inside it) will depend on which style guide you are asked to use. MLA, APA, Associated Press, Chicago, and all other style guides each have slightly different requirements for citations.

If you don’t own the actual style guide (I know, not everyone has the 7th Edition of the APA Style Guide sitting on their bookshelf…but now you know what to ask for this Christmas!), my favorite resource is Purdue Online Writing Lab (OWL), which gives tons of information about how to cite different sources for each style.

Numerical Lists

Numerical lists that are set in a paragraph (not separated) use numbers that are enclosed in parentheses. This is one function that is unique to parentheses—there’s no other grammatically correct way to incorporate a numbered list into a paragraph.

When writing your research paper, be sure to (1) interview an expert, (2) describe your experiment in detail, and (3) display your results in a chart or graph.

You can use letters instead of numbers, if you prefer:

He asked me if I wanted (a) soup, (b) a sandwich, or (c) both.

Writing a numbered or lettered list and NOT enclosing the numbers or letters in parentheses is incorrect:

When writing your research paper, be sure to 1. interview an expert, 2. describe your experiment in detail, and 3. display your results in a chart or graph.

When writing your research paper, be sure to 1) interview an expert, 2) describe your experiment in detail, and 3) display your results in a chart or graph.

When writing your research paper, be sure to (1) interview an expert, (2) describe your experiment in detail, and (3) display your results in a chart or graph.

If you are setting the list apart as its own “paragraph,” you don’t need the parentheses:

The options for lunch were as follows:

1. soup
2. salad
3. sandwich

Mathematical Material

You might see parentheses used as part of equations in mathematical research papers. When used this way, parentheses function mathematically and not grammatically, meaning you should insert them wherever they need to go in order for the math to be correct.

Here’s a quick example:

We used the equation (k-1)/(g-2) to find the necessary value.

WARNING: Avoid These Common Mistakes

Mistake #1: Putting Parentheses in the Wrong Place

Whatever goes inside the parentheses should have no grammatical relationship to the rest of the text, meaning you should be able to completely remove it without causing grammatical errors in the surrounding writing.

Let’s go back to this example:

Snow White worked hard and was cheerful (but the Evil Queen treated her poorly).

If I removed the parenthetical statement, I’d get this completely grammatically correct sentence:

Snow White worked hard and was cheerful.

However, if I moved around the parentheses like this…

Snow White worked hard and was cheerful but (the Evil Queen treated her poorly).

…then removing the parenthetical statement leaves me with this confusing—and grammatically incorrect—sentence:

Snow White worked hard and was cheerful but.

Whenever you insert parentheses into your writing, make sure you can completely remove the parentheses along with everything inside them and your writing still makes sense.

Imagine that a crane is coming along, hooking up to those curved parentheses, and pulling them out of your sentence. If that happens, does it destroy your grammar or meaning? If so, you need to revise so that your parenthetical statements are (1) not essential to the meaning of the writing and (2) not grammatically connected to the surrounding text.

Mistake #2: Incorrect End Punctuation

Remembering Mistake #1 will help you avoid Mistake #2. Make sure that any punctuation that is essential to the surrounding text goes OUTSIDE the parentheses, but any punctuation that is only relevant to the parenthetical statement is INSIDE the parentheses.

When there’s a complete sentence inside parentheses and that sentence is NOT inserted within another sentence, you should include all punctuation inside those parentheses.

George pedaled his bicycle down the street. (He didn’t have to go far.)

However, if there’s a complete sentence inside parentheses and those parentheses are INSIDE another sentence, you do NOT need a capital letter or ending punctuation within your parentheses.

George pedaled his bicycle down the street (he didn’t have to go far).

Remember that you should be able to pull out the parentheses and everything inside them and not cause any problems. If a sentence’s end punctuation is stranded inside the parentheses, you could lose it! For example, if we wrote this…

George pedaled his bicycle down the street (he didn’t have to go far.)

…then when we took out the parenthetical statement, our sentence would suddenly lose its period!

George pedaled his bicycle down the street

We could also test out this parentheses-disappearing act with parenthetical statements that are not part of another sentence. If we write a sentence like this…

George pedaled his bicycle down the street. (He didn’t have to go far).

…and try to take out that parenthetical statement, suddenly we have DOUBLE periods because we left one out of the parentheses.

George pedaled his bicycle down the street. .

In short, when a complete sentence is enclosed in parentheses and is NOT part of another sentence, place end punctuation INSIDE the closing parenthesis. When a complete sentence, phrase, or word is enclosed in parentheses and IS part of another sentence, place end punctuation OUTSIDE the closing parenthesis.

I’ve listed a bunch of examples to illustrate how parentheses should work with punctuation and capitalization.

Capitalization for parenthetical statements within a sentence:

We crept down the hallway (Keeping entirely silent) to avoid being caught.

We crept down the hallway (keeping entirely silent) to avoid being caught.

Punctuation belonging only to the parenthetical statement (not the the full sentence):

Send your RSVP (today, please)! to Jessica.

Send your RSVP (today, please!) to Jessica.

End punctuation for a parenthetical statement that IS within another sentence:

Jamie prefers large dog breeds (e.g., German Shepherds, Golden Retrievers, and Great Danes.)

Jamie prefers large dog breeds (e.g., German Shepherds, Golden Retrievers, and Great Danes).

End punctuation and capitalization:

Leslie entered the room cautiously (She wasn’t sure if it was the right one.).

Leslie entered the room cautiously (she wasn’t sure if it was the right one).

End punctuation for a parenthetical statement that is NOT within another sentence:

There were several prom dresses on the rack, but she still couldn’t find one she liked. (At this rate, she’d never be ready in time).

There were several prom dresses on the rack, but she still couldn’t find one she liked. (At this rate, she’d never be ready in time.)

Mistake #3: Nested or Back-to-Back Parentheses

Most style guides will tell you to AVOID using parentheses within parentheses (also called “nested parentheses”). If there’s no avoiding it, you should use square brackets for the nested set of parentheses:

My boss was upset that I didn’t finish the report earlier (I told her I’d get it done by the end of the day (EOD) to make up for its tardiness).

My boss was upset that I didn’t finish the report earlier (I told her I’d get it done by the end of the day [EOD] to make up for its tardiness).

Additionally, you should avoid having parenthetical statements that run into each other:

Active working dogs need plenty of stimulation (e.g., walks, playtime, and enrichment activities) (that’s why they don’t make great apartment pets).

To fix this, you can either reword your sentence…

Active working dogs need plenty of stimulation, like walks, playtime, and enrichment activities (that’s why they don’t make great apartment pets).

…or use a semicolon to combine your parenthetical statements.

Active working dogs need plenty of stimulation (e.g., walks, playtime, and enrichment activities; that’s why they don’t make great apartment pets).

Mistake #4: Clutter

Using too many parentheses can cause clutter in your writing. If you notice that the parentheses seem to be piling up, try to use other interrupters (like commas or dashes) or just cut out unimportant information. If the information inside the parentheses is actually important, you should incorporate it cohesively into your writing rather than hiding it away in parentheses.

Parentheses are a handy tool that can help you add fun tidbits, extra info, and helpful examples in your writing! They’re like the nooks and crannies of an old house: they’re a bit hidden and out of the way, but they often contain the best surprises.

Drop any questions you have about parentheses in the comments, and I’ll find you an answer!

Sources:

• American Psychological Association. Publication Manual of the American Psychological Association. 7th ed. Washington, DC: American Psychological Association, 2020.
• The Chicago Manual of Style. 17th ed. Chicago, IL: The University of Chicago Press, 2017.
• Ebbitt, D. R., and W. R. Ebbitt. Index to English. 8th ed. New York: Oxford University Press, 1990.
• Einsohn, Amy. The Copyeditor’s Handbook. 3rd ed. Berkeley and Los Angeles, California: Univ of California Pr, 2011.