Punctuation marks are a written convention that make reading and writing clearer by ensuring the clarity of written language. There are four rules for using parentheses as punctuation marks in written American English:
- Enclose numbers and letters in a list
- Enclose clarifications
- Enclose emphasizations
- Enclose asides and additional information
The following sections explain and provide examples of the punctuation rules for parentheses in written English.
Enclose Numbers and Letters in a List
Use a set of parentheses to enclose the numbers or letters in a list that is part of the grammatical structure of the sentence or that follows a colon. For example:
- Relative pronouns function as (1) subject, (2) direct objects, (3) prepositional complements, (4) possessive determiners, and (5) adverbials in English grammar.
- All applicants must return the following materials by January 30: (a) resume or CV, (b) personal statement, (c) three letters of recommendation, and (d) all prior transcripts.
Use a set of parentheses to enclose a clarification. For example:
- Please review the report (Exhibit A) before today’s meeting.
- Books marked IRMA (Infrequently Requested Materials Area) may be checked out.
Use a set of parentheses to introduce an emphasization with a moderate level of emphasis. For example:
- Many people are afraid of sharks (although attacks by other animals like dogs are more probable).
- The library (the six-story building next to the student center) is open twenty-four hours during finals week.
Do not use parentheses to introduce an emphasization with a high level of emphasis.
Enclose Asides and Additional Information
Use a set of parentheses to enclose an aside or some other additional information that is not part of the grammatical structure of the sentence. For example:
- New students (mostly freshmen but some transfer) need information about available parking.
- My daughter (she goes to Illinois State) plans to become a teacher-nurse.
Do not use parentheses to enclose information that is part of the grammatical structure of the sentence.
Punctuation is a convention of written language that helps readers and writers more clearly understand writing by ensuring clarity. Parentheses perform four basic functions in written American English: enclose numbers and letters in a list, enclose clarifications, introduce emphasizations, enclose asides and additional information.
For information on the use of dashes—a punctuation mark that is closely related to the parenthesis—in written American English, please read the article Punctuation Rules for Dashes in Written English.
Faigley, Lester. 2003. The Brief Penguin Handbook. New York: Pearson Longman.
Gibaldi, Joseph. 2003. MLA Handbook for Writers of Research Papers. 6th ed. New York: The Modern Language Association of America.