A serial comma simply means that a comma will separate each element in a series of three or more, even before the coordinating conjunctions and and before or. The following are simple examples of serial commas:
Lions, tigers, and bears.
Apples, oranges, and bananas.
Morning, afternoon, or night.
Here is an example of a serial comma used within a sentence:
There has never before been such widespread focus in the educational community on early childhood teacher quality, standards, and accountability (Scott-Little, Lesko, Martella, & Milburn, 2007).
Additionally, note that serial commas should also be used to separate authors’ names in parenthetical and in-text citations and reference list entries. Thus, while the serial comma is used for the list within the sentence above, it is also used to separate the authors’ names in the parenthetical citation.