Parentheses [( )] enclose information, such as asides, examples, or explanations. The information inside a set of parentheses is considered nonessential, meaning you can remove the information without changing the meaning of the sentence (though the information may be helpful or interesting to the reader).
Here are 13 examples of when to use parentheses:
1. To enclose nonessential information
She finally stepped onto the plane (having taken over an hour to conquer her fear of flying).
John dashed from the room (having completely lost his nerve) and ran home.
Note: If the text in parentheses is not a complete sentence and comes at the end of a line, as in the first example, the period is placed after the parentheses.
2. To enclose dates
David Bowie (1947–2016) was an English musician whose successful career spanned five decades.
During World War II (1939 –1945), millions of civilians lost their lives in air raids.
4. To create in-text citations in an academic work
Other scholars, including Angela Brooks, have noted that Virginia Woolf was a feminist pioneer (Brooks 134).
The art critic Peter Wills has called Vincent van Gogh the “greatest artist of all time” (Wills, 2012, p.49).
5. To show time zones
Bob will arrive in Britain at 10:00am (GMT).
This plane will land at 11:00am (EST).
6. To enclose letters or numbers in a horizontal list
Before the interview, please submit the following items: (1) your passport, (2) your driver’s license, and (3) your health insurance card.
Customer check-in process: (a) take a ticket, (b) find a seat in the lobby, and (c) wait for your name to be called.
7. To introduce acronyms and abbreviations
John landed a job with the Federal Emergency Management Agency (FEMA). FEMA was the last place John expected to find a job.
George held a Bachelor of Arts (BA) degree.
8. To show area codes
Call me internationally at (111) 534-9034.
My phone number is (602) 242-1515.
10. To indicate a possible plural
Place a check mark next to the correct answer(s).
Please report the person(s) who graffitied the wall.
11. To create mathematical expressions
3y = 2(2+2Y)
(1 x² + 2 x²) + (4 x² + 3 x²)
12. To show translations
Jack knew how to say hello (hola) in Spanish.
Adieu (farewell) is a parting saying in French.
13. To re-state a number
The deadline before repossession is nineteen (19) days.
Your first payment is due in ten (10) days.
Note: only use parentheses to re-state a number in formal writing, such as legal, business or scientific writing. Re-stating numbers in less formal contexts is usually unnecessary and likely to distract your readers.
Reminders
Remember that parentheses are not part of the subject in a sentence.
Incorrect: Emma (and her cat) were very skinny.
Correct: Emma (and her cat) is very skinny.
If this seems awkward, simply rewrite the sentence without using parentheses.
Emma and her cat are very skinny.
In most cases when a set of parentheses is part of a sentence, terminal punctuation goes outside the parentheses.
The dog ran away (for the third time).
But if the information in the parentheses is a question or exclamation, place the punctuation mark within the parentheses.
The dog ran away for the third time (is he trying to tell me something?), which means I should expected another angry call from my neighbor with the vegetable garden.
Judy stepped outside and saw her demolished vegetable garden (her brand new vegetable garden!), and ran inside for the phone.