Parentheses

Parentheses ( ) are used to enclose nonessential or supplemental information in a sentence. Parentheses are always used in pairs; you must have both an opening and a closing parenthesis.

In formal academic writing, it is a good practice to use parentheses sparingly. Before including parentheses, check to see if they are essential. Could the information in parentheses be included as a subordinating clause surrounded with commas? Could the information in parentheses be a stand-alone sentence? If parentheses are needed, keep the following rules in mind.

1. Use parentheses around nonessential information or abrupt changes in thought.
   • When the words in parentheses form a complete sentence, place a period inside the closing parenthesis.
     • No personal phone calls are allowed on company time. (Refer to the policy manual.)
   • When the words in parentheses are not a complete sentence, place the period outside the closing parenthesis.
     • The meeting will be held next year (in March).
   • Always place commas, semicolons, and colons outside the closing parenthesis.
     • The tasks consist of filling out paper work (including HR documents), setting up your email account, and getting a photo ID.
2. If the information in parentheses requires a question mark or an exclamation mark, use the mark inside the parentheses only if the sentence ends with a different mark.
   • Richard Bender (remember him?) stopped by to see me yesterday.
   • Do you remember Richard (think you can remember back that far) from the bank?
3. Use parentheses to clarify preceding words.
   • Next week we will study the hydrologic cycle (also known as the water cycle).
4. Use parentheses for references or documentation of sources.
   • Fifty contracts were issued this year. (See Table 1.)
   • The U.S. leads the world in Internet use (Leslie 89).
5. Use parentheses around an abbreviation or an acronym when it is used with the spelled–out word.
   • Please submit the Student Aid Report (SAR).
6. Use parentheses in a horizontal list of items that uses either letters or numbers.
   • I need three items from the store: (1) apples, (2) bread, and (3) milk.
   • The following information must be included: (a) name, (b) address, and (c) driver's license number.
7. Capitalize the first word in parentheses if it is a proper noun or the beginning of a complete sentence.
   • Verify all items. (Check the boxes.)
   • Call the assistant (Robert Digg) at noon.
8. Use parentheses around numerals used with a spelled–out number.
   • I have ninety (90) dollars left from my paycheck.
9. Use parentheses for minor subdivisions in alphanumeric outlines.
   • I.
     A.
     B.
     1.
     2.
     a.
     b.
     (1)
     (2)
     (a)
     (b)
     II.