Punctuation is a written convention that makes reading and writing clearer by ensuring the clarity of written language. There are five rules for using brackets as punctuation marks in written American English:
- Inside parentheses
- Clarification in quotations
- Indicate errors in quotations
- Revise quotations
- Indicate word origin
Use a set of brackets to enclose parenthetical information that appears inside other parenthetical information that is enclosed by parentheses. For example:
- The author (Charles Dickens [1812-1870] was paid by the word) wrote many, lengthy novels.
- (Harry Potter [the teacher, not the fictional character] is up for an award.)
Do not use brackets to enclose a single layer of parenthetical information.
Clarification in Quotations
Use a set of brackets to provide clarification of information inside quotation marks. For example:
- Ron replied, “He [Hagrid] has been missing all semester.”
- And I quote from the employee handbook: “One [a new employee] must register all vehicles with the travel unit.”
Indicate Errors in Quotations
Use a set of brackets around the abbreviated Latin expression [sic], a phrase that literally means “thus in the original,” to indicate an error inside a quotation. For example:
- “There are six mispelings [sic] in your article,” wrote the overly pompous editor.
- “You can take all the sincerity in Hollywood, place it in the navel of a firefly, and still have room enough for three caraway seeds and a producers [sic] heart.”
Use a set of brackets around a revision to revise information in a quotation. For example:
- The instructions indicate that “add[ing] too much cream will make the pie too thick.”
- “Use [brackets] to revise a quotation.”
Indicate Word Origin
Use a set of brackets to indicate information of the language of origin of a word. For example:
- breviate [L.]
- Zeitgeist [G.]
Punctuation marks are 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: inside parentheses, clarification in quotations, indicate errors in quotations, revise quotations, and indicate word origin.
For information on the use of parentheses and dashes—punctuation marks that are closely related to the brackets—in written American English, please see Punctuation Rules for Parentheses in Written English and 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.