The serial comma, also known as an Oxford comma, appears before the last item in a list of three or more items (American Psychological Association, 2020, p. 155). The 7th edition of the Publication Manual of the American Psychological Association requires authors to include serial commas; see page 155 in the 7th edition manual for information.
Example:
Correct: The stripes on the book are black, orange, and yellow.
Incorrect: The stripes on the book are black, orange and yellow.
Reference
American Psychological Association. (2020). Publication manual of the American Psychological Association (7th ed.). https://doi.org/10.1037/0000165-000
