A period ends a complete sentence (American Psychological Association [APA], 2020, p. 154).
Confusion regarding whether a period should appear inside or outside closing quotation marks is usually caused by conflicting styles between American and British authors. The American style, which is reflected in the APA Style rules, presents the period inside the quotation marks (APA, 2020, p. 157); e.g., most participants chose “yes.” In contrast, the British style places the period outside the quotation marks (Lee, 2011, para. 3); e.g., most participants chose "yes".
If the quoted text is a direct quotation of 39 words or fewer and therefore has a citation after the closing quotation marks, the period appears after the citation (APA, 2020, p. 271). For example, “if the citation appears at the end of a sentence, put the end punctuation after the closing parenthesis for the citation" (APA, 2020, p. 271).
If the quotation is 40 words or longer and will be formatted as a block quotation, place the period at the end of the quotation and before the citation (APA, 2020, p. 272). For example:
Compositors―people who layout printed material with type―made the original rule that placed periods and commas inside quotation marks to protect the small metal pieces of type from breaking off the end of the sentence. The quotation marks protected the commas and periods. In the early 1900s, it appears that the Fowler brothers (who wrote a famous British style guide called The King’s English) began lobbying to make the rules more about logic and less about the mechanics of typesetting. They won the British battle, but Americans didn’t adopt the change. (Fogarty, 2013, p. 1)
Per the 7th edition APA Style rules, insert one space after a period (APA, 2020, p. 154). To check for consistent spacing, take advantage of Microsoft Word’s grammar and style check, which will look for one or two spaces between sentences:
For instructions on turning on Word's grammar and style check, please see Check Grammar, Spelling, and More in Word.
Within references, a period should always be followed by one space (APA, 2020, p. 154).
According to the APA Style rules, periods should not be used in the following instances:
American Psychological Association. (2020). Publication manual of the American Psychological Association (7th ed.). https://doi.org/10.1037/0000165-000
Fogarty, M. (2013, December 23). How to use quotation marks [Blog post]. Retrieved from http://www.quickanddirtytips.com/education/grammar/how-to-use-quotation-...
Lee, C. (2011, August 11). Punctuating around question marks [Blog post]. Retrieved from http://blog.apastyle.org/apastyle/2011/08/punctuating-around-quotation-m...