Parentheses (always used in pairs) allow a writer to provide additional information. The parenthetical material might be a single word, a fragment, or multiple complete sentences.
Whatever the material inside the parentheses, it must not be grammatically integral to the surrounding sentence. If it is, the sentence must be recast. This is an easy mistake to avoid. Simply read your sentence without the parenthetical content. If it remains grammatically correct, the parentheses are acceptable; if it doesn’t, the punctuation must be altered.
Correct Example:
The committee (including the treasurer) will meet next week.
Incorrect Example:
The committee (including the treasurer) is making important decisions today.
Placement of Other Punctuation
When a parenthetical sentence stands on its own, the closing punctuation mark for the sentence is placed inside the closing parenthesis.
Example:
The concept of emotional intelligence is critical in leadership roles. (But not all leaders embrace it.)
When parenthetical content occurs at the end of a larger sentence, the closing punctuation mark for the sentence is placed outside the closing parenthesis.
Example:
The team achieved a major milestone (a breakthrough in research).
When parenthetical content occurs in the middle of a larger sentence, the surrounding punctuation should be placed outside the parentheses, exactly as it would be if the parenthetical content were not there.
Example:
The project was completed ahead of schedule (thanks to diligent teamwork), but the budget exceeded expectations.
When a complete sentence occurs in parentheses in the middle of a larger sentence, it should neither be capitalized nor end with a period—though a question mark or exclamation point is acceptable.
Example:
The report was thorough (we really put in the effort) and provided actionable insights (which the team greatly appreciated!).
Specialized Uses
Numbered or lettered lists should use a pair of parentheses to enclose the numbers or letters.
Example:
Please review the following documents: (1) the financial report, (2) the project proposal, (3) the meeting agenda, and (4) the attendance record.
Time zones are usually enclosed in parentheses following the time.
Example:
The webinar will start at 3:00 p.m. (PST).
Area codes are sometimes enclosed in parentheses.
Example:
For more information, call (555) 123-4567.
Short translations in unquoted text can be placed in parentheses. (Use brackets for translations in quoted text.)
Example:
His favorite phrases in Italian are buongiorno (good morning) and arrivederci (goodbye).
In some writing, a person’s year of birth and year of death are provided in parentheses when the person is first mentioned. If there is uncertainty about the year, a question mark should follow it. Note that an en dash, rather than a hyphen, is used between the years.
Example:
Virginia Woolf (1882–1941) was a prominent figure in modernist literature.
Abbreviations and Acronyms
On the first use of an abbreviation or acronym that might not be understood by your readers, the full term can be provided in parentheses.
Example:
The new regulations will be enforced by the Environmental Protection Agency (EPA).
In reverse, an acronym or abbreviation can be provided in parentheses upon its first use, and then used in place of the full term in the remainder of the document.
Example:
Researchers utilized advanced imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI), to enhance diagnosis.