By Jennifer Copley (Last Updated, November 26, 2013)
Everyone knows that you typically use a period at the end of a sentence, but there are times when the period is not needed. Don’t add a period:
- When a sentence ends with an abbreviation such as U.S. that contains a period
- After question marks (?) and exclamation marks (!)
- After ellipses (. . .) that are used to indicate a thought trailing off
- After list items that are not full sentences (unless working with a style guide that requests them)
Periods with Other Punctuation
The following rules govern the use of periods with other types of punctuation:
- If writing for North American readers, place periods inside quotation marks: Bertha said, “my accordion was run over by a train.” (In the UK, placement of other punctuation with quotation marks is more complex. See the Oxford Guide to Style’s for more information.)
- If using footnotes, add the numbers after the periods: Her theory was supported by research linking storm frequency to picnic plans.1
- If using in-text citations, add the punctuation after the reference in parentheses: Research indicates that cats have no interest in solving complex algebraic equations (Squigglepuss & Knickerbocker, 2008).
- When adding parenthetical phrases:
- Don’t add periods after parenthetical sentences or phrases in the middles of sentences: A monkey in a top hat (although he looks quite dapper) is still a monkey.
- When a parenthetical phrase occurs at the end of the sentence, put the period outside the parentheses: A monkey in a top hat is still a monkey (although he looks quite dapper).
- If a full sentence is placed in parentheses after a full sentence outside the parentheses, place a period inside the parentheses: A monkey in a top hat is still a monkey. (However, he looks quite dapper.)
- American Psychological Association. (2011). “Punctuating Around Quotation Marks.” Blog.APAStyle.org.
- Brians, P. (n.d.). Common Errors in English Language.
- Capital Community College Foundation. (n.d.). “Quotation Marks” and “Commas.” Grammar.ccc.commnet.edu.
- Fogarty, M. (2010). Grammar Girl: Quick and Dirty Tips.
- O’Conner, P. T. (1996). Woe Is I, the Grammarphobe’s Guide to Better English in Plain English. New York, G. P. Putnam’s Sons.
- OWL at Purdue. (2013). “How to Use Quotation Marks” and “Extended Rules for Using Commas.” The Writing Lab & the OWL at Purdue and Purdue University. OWL.English.Purdue.edu.
- Strauss, J. (2013). Grammarbook.com.
- The Guardian. (2013). “‘The British style’? ‘The American way?’ They are not so different.” TheGuardian.com.
- Trask, L. (1997). Guide to Punctuation. University of Sussex.