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A serial comma (also called the Oxford comma) is the comma placed immediately before the coordinating conjunction (usually "and" or "or") in a series of three or more items. The serial comma is required in APA style for clarity and consistency.

Serial Comma Examples

The following sentences include serial commas:

  • The final portfolio should demonstrate critical thinking, clear writing, research abilities, and practical application.
  • The advancement program includes resume writing, interview preparation, networking skills, and salary negotiation.
  • Many students balance their coursework with full-time jobs, family responsibilities, and community commitments.

 

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In each of these examples, notice the comma before "and" in the list; that final comma is the serial comma.

Why the Serial Comma Matters
Using (or omitting) the serial comma can change the meaning of a sentence and make all the difference in avoiding confusion!

Example

I'd like to thank my parents, Alex Trebek and Betty White.

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Without the serial comma, this could be read as though your parents are Alex Trebek and Betty White. If that is not the intention, adding the serial comma enhances clarity.

Possible Revision

I'd like to thank my parents, Alex Trebek, and Betty White.

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Now it's clear that this is a list that includes:

  1. my parents
  2. Alex Trebek
  3. Betty White

Additional Uses and Rules 

Items in a Series that Contain Commas

If any items in the series contain commas, use semicolons to separate them instead.

The following sentence demonstrates this rule:

  • The team includes John Smith, Marketing Director; Sarah Chen, Project Manager; and David Lee, Senior Developer.

In this example, there are already commas between a person’s name and their title.

Using additional commas could create confusion about where one person’s information begins and ends. Using semicolons instead of commas helps readers clearly distinguish between each person in the list.

Reference Lists

Serial commas should also be used to separate authors’ names in reference list entries.

Bir, C., Croney, C. C., & Olynk Widmar, N. J. (2019). US residents' perceptions of dog welfare needs and canine welfare information sources. Journal of Applied Animal Welfare Science, 22(1), 42-68. https://doi.org/10.1080/10888705.2018.1476862

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