Periods are used to end sentences or to separate letters in some abbreviations.

Use a period...

  1. To end a complete statement, a command, an indirect question, or a polite request

    A statement
    • The benefits include stock options.
    A command
    • Organize these jobs based on the deadlines.
    An indirect question
    • She asked for directions to the site.
    A polite request
    • Will you please be on time for work.
    If a sentence ends with a citation, place the period after the citation NOT inside it.
    • After 2007, differentiation become more popular (McInerney, 2016).

  2. In most abbreviations or acronyms that contain lowercase letters

    If the abbreviation is at the end of a sentence, use only one period. Omit the periods in the initials of government agencies, companies, radio and television stations, some professional designations, and well–known people. Some abbreviations written in all capital letters may be written without periods.
    • The guides were published by ABC, Inc.
    • In five years, I plan to return to school for a Ph.D.
    • The seminar was led by Robert Sanchez, CPA.

  3. After a person's initial

    • Mr. Brian P. Neal is president of the company.
    • George R. R. Martin wrote the Game of Thrones books. 

  4. After a complete sentence in a list

    • Two workable solutions were presented:
      1. Continue along the present course of action.
      2. Make the changes the consultant suggested.
    • Two workable solutions were presented:
      1. Continue 
      2. Make changes 

  5. In outline numbering

    Include periods after letters and numbers in an alphanumeric outline, except those enclosed in parentheses. Use periods to separate levels of headings in a numeric outline.

  6. In a decimal and between dollars and cents

    • .050
    • 1.5
    • $1.50
    • $0.50

  7. In an ellipsis

    Use periods in an ellipsis (a series of three periods with a space before, between, and after the series) to show that something has been omitted from quoted material. If the omission includes a complete sentence, add a fourth period to the ellipsis to indicate the period at the end of the sentence.
    • Jon said, "I was ready to ship the product . . . packing material was not available."
    • Margaret stated, "I have several key issues . . . . When will the package arrive?"

  8. After the p or para in an in-citation for a quote

    • (Smith, 2015, p. 45)
    • (Jones, 2017, para. 9)