Oxford Comma — Definition, Examples, and Rules
What is the Oxford comma?
The Oxford comma is the final comma placed between the last two items in a series of three or more. It precedes the conjunction "and" or "or."
The punctuation mark was named after its use by the Oxford University Press, but it is commonly referred to as a serial comma or Harvard comma.
The Oxford comma, the last comma at the end of a list, helps writers maintain clarity and effective sentence structure:
Ambiguity: Without including a serial comma, the information provided in a sentence may be unclear or change the meaning of a sentence.
This book is dedicated to my parents, Ayn Rand and God.
Without the Oxford comma, the sentence suggests the writer’s parents are Ayn Rand and God. The inclusion of the comma would appropriately recognize three different people.
Cadence: The use of the Oxford comma helps the reader pause after each item in the series, which helps create a natural rhythm and pace for the reader.
Connection: A lack of a comma can create an unnecessary connection between the last two items.
The fundraiser included John Smith, a politician and an actor.
Without the Oxford comma, the sentence suggests John Smith is an actor and politician. The inclusion of the serial comma would help the reader identify three individuals.
Oxford comma rules
Since the Oxford comma is a stylistic choice, there are no specific grammatical guidelines. However, when utilizing the Oxford comma, most style guides lay out the following rules:
Placement: Place the comma before the conjunction used to identify the last item in the list:
Correct: He wanted to go to the zoo, park, and museum.
Incorrect: He wanted to go to the zoo, park and museum.
Number of items: If only two items make up the list, a serial comma is unnecessary.
Correct: Reading and writing are two of his favorite hobbies.
Incorrect: Reading, and writing are two of his favorite hobbies.
Style Guide: Determining whether or not to use the Oxford comma depends on what style manual the writer uses. The following style guides require the use of a serial comma:
MLA: The Modern Language Associate (MLA) style is used within the humanities (literature, language arts, cultural studies).
Chicago: Writing that focuses on business, history, and the fine arts uses the Chicago manual of style.
APA: The social sciences (psychology, sociology, criminology) use the American Psychological Association (APA) style.
AP style Oxford comma
Unlike the MLA, Chicago, and APA style manuals, the Associated Press (AP) style manual, commonly used amongst journalists, does not require the Oxford comma. However, those writing using the AP stylebook are not forbidden to use it. If not using a serial comma would lead to confusion or ambiguity, then it should be used.
Oxford comma examples
The following sentences contain a list of items that successfully incorporate the Oxford comma:
Siobhan wasn't sure if she should take English, math, or science first thing in the morning.
Addison enjoyed the amusement park so much that he wouldn't leave until he rode the roller coaster, carousel, and log flume one last time.
Annie remembered to pick up the eggs, butter, sugar, and flour needed to make the cookies for the bake sale.
Lucas didn't remember if he was supposed to take a left, turn right, or stay straight.
Ava thought of four names for her new puppy: Baloo, Casper, Domino, and Max.