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Grammar and Mechanics: Commas

Comma Basics

Commas are punctuation marks with a variety of uses. See APA 7, Section 6.3 for more information and examples.

Note the bolding and highlighting used for emphasis in the examples on this page.

The following constructions require commas:

  1. Lists. In a list with three or more elements, use commas to separate all of the elements of the series. This punctuation rule is also followed for parallel structure in a series.

    Example: In this chapter, I describe the purpose of the study, the research questions, and the theoretical framework.

    Example: I collected data through semistructured interviews, classroom observations, and the state’s standardized test scores.

  2. Nonessential clauses. Use commas to set off clauses that contain information that is nonessential to the sentence's meaning. For more information, view the page on relative, restrictive, and nonrestrictive clauses

    Example: The Stetler model, first developed in 1976 and updated in 2001, can be used to explore evidence-based nursing practices.

    Note that without the middle clause (first developed in 1976 and updated in 2001), the sentence still makes sense (The Stetler model can be used to explore evidence-based nursing practices). Therefore, the clause is nonessential.

    Example: Small businesses in the United States, usually defined as having fewer than 500 employees, make up a high percentage of U.S. employer firms.

    Note that without the middle clause (usually defined as having fewer than 500 employees), the sentence still makes sense (Small businesses in the United States make up a high percentage of U.S. employer firms). Therefore, the clause is nonessential.

  3. Compound sentences. Use a comma to separate two independent clauses connected by a coordinating conjunction. A coordinating conjunction is a connecting word such as and, but, or or. For more information, view the page on sentence structure and types of sentences.

    Example: Novice teachers often implement teaching strategies that are familiar to them, and they may believe that teacher-centered instruction is the easiest way to prepare their lessons.

    Example: Participants could choose to meet me at their place of employment, or they could choose to meet in a quiet reserved room at the local library.

  4. After a dependent introductory clause, phrase, or word. Use a comma after a dependent introductory clause, phrase, or word.
    Example of introductory phrase: Before completing the interviews, I obtained Walden University IRB approval.
    Example of introductory phrase: To address this problem, I developed a 3-day professional development workshop.
    Example of introductory word: Therefore, I created three research questions.
    Example of introductory word: However, further research is needed.
  5. Dates. Use a comma to set off the year in exact dates.
    Example: Data collection closed on March 15, 2018.
  6. Citations. Use commas to set off the elements of a citation.
    Example: When comparing undergraduate- and graduate-level writing, “abstracts by PhD-level students better approximated those of expert writers” (Ansarifar et al., 2017, p. 67).
  7. Introducing quotations (not seamless). Use a comma when an independent clause introduces a quotation but is not seamlessly integrated into it. The APA Style Blog has a post on this as well.
    Example: Cooley and Lewkowicz (2003) stated, “Although the abstract is the last part of a dissertation to be written, it is generally one of the first the reader will look at” (p. 112).
    Example: Paltridge and Starfield (2007) asserted, “There is no single right way in which to organize the review of the literature” (p. 101).

 

Common Comma Errors

The following constructions do not require commas:

  1. Months. Do not use a comma when referring to a month within a particular year.
    INCORRECT:
    I conducted the study in June, 2018.

    CORRECT:
    I conducted the study in June 2018.
  2. Compound predicate. Do not use a comma between two parts of a compound predicate (In other words, there is one subject for the sentence but more than one predicate.) These parts are often connected with a conjunction such as andor, and but.
    INCORRECT:
    Smith (2017) found that results were consistent, but also suggested further investigation.

    CORRECT:
    Smith (2017) found that results were consistent but also suggested further investigation.
  3. Introducing quotations (seamless). Do not use a comma when the quotation is integrated into the sentence. This is often the case with that clauses.
    INCORRECT:
    Paltridge and Starfield (2007) asserted that, "there is no single right way in which to organize the review of the literature" (p. 101).

    CORRECT:
    Paltridge and Starfield (2007) asserted that "there is no single right way in which to organize the review of the literature" (p. 101).
  4. Comma splices. A comma splice is a type of run-on sentence that occurs when two independent clauses (complete sentences) are separated by just a comma.
    INCORRECT:
    The results of the study showed that teachers want more support in giving written feedback, these results were similar to those of many previous researchers.

    CORRECT (use a period):
    The results of the study showed that teachers want more support in giving written feedback. These results were similar to those of many previous researchers.

    CORRECT (use a semicolon):
    The results of the study showed that teachers want more support in giving written feedback; these results were similar to those of many previous researchers.

    CORRECT (use a comma and a coordinating conjunction):
    The results of the study showed that teachers want more support in giving written feedback, and these results were similar to those of many previous researchers.