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Punctuation: Periods

Period Basics

Periods are punctuation marks used to separate sentences or elements of reference lists. Use a period in the following instances.

  1. To end a complete sentence.
    Example: Johnson (1998) claimed that he had cured cancer.
  2. To end a sentence that includes a citation or a quotation. Note the placement of the period in the following instances.
    Example: It was clear that Hong Kong had been culturally colonized by the West (Gouper & Finn, 1987).
    Example: Boomer and Watts (2003) insisted that "there was little that could save NATO in its current state" (p. 54).
  3. To end a block quotation (before the citation). Note the placement of the period in the following example (different than the second example above).
    Example: Vonnegut (1965) believed that

    All time is all time. It does not change. It does not lend itself to warnings or explanations. It simply is. Take it moment by moment, and you will find that we are all, as I've said before, bugs in amber. (p. 65)

  4. Between elements of reference list entries.
    Example: Smith, J. (2009). Best book ever. New York, NY: HarperCollins.

Refer to section 4.02 of the APA manual for more information about the use of periods.

Misuses of Periods

Periods are not necessary when using acronyms.

Example: My instructor told me to consult my A.P.A. manual.