What Is the Oxford (or Serial) Comma?

A Primer on the Fiercely-Debated Punctuation Rule

The Three Stooges: Moe, Curly, and Larry (with an Oxford comma in front of and). (Columbia Pictures/Getty Images)

The Oxford comma is the comma that precedes the conjunction before the final item in a list of three or more items:

  • This song was composed by Moe, Larry, and Curly.
  • This website is devoted to Moe, Larry, Curly, Shemp, Joe, and Curly Joe.
  • This book is dedicated to my roommates, Beyoncé, and God.

The Oxford comma is so called because it has traditionally been used by editors and printers at Oxford University Press.

("To call it the Oxford comma gives it a bit of class," says copy editor Mary Norris. "Chances are that if you use the Oxford comma you brush the crumbs off your shirtfront before going out."*) New Englanders may favor the term Harvard comma (the convention is also followed by Harvard University Press). Throughout the U.S. the mark is commonly called the serial comma.

When Should We Use the Oxford Comma?

Most U.S. style guides say, "Use it--always." Garner's Modern American Usage (Oxford, 2009) makes the standard case for clarity:

Whether to include the serial comma has sparked many arguments. But it's easily answered in favor of inclusion because omitting the final comma may cause ambiguities, whereas including it never will.

Likewise, The Chicago Manual of Style (2010) "strongly recommends" using the serial comma because "it prevents ambiguity":

If the last element consists of a pair joined by and, the pair should still be preceded by a serial comma and the first and:
  • The meal consisted of soup, salad, and macaroni and cheese.
  • John was working, Jean was resting, and Alan was running errands and furnishing food.

Most college writing handbooks in the U.S. also advocate use of the serial comma.

But not The Associated Press Stylebook (2010), which determines usage at most American newspapers:

Use commas to separate items in a series, but do not put a comma before the conjunction in a simple series: The flag is red, white and blue. He would nominate Tom, Dick or Harry.

But the AP Stylebook (which is always looking for excuses to save space) does qualify this precept:

Put a comma before the concluding conjunction in a series, however, if an integral element of the series requires a conjunction: I had orange juice, toast, and ham and eggs for breakfast.

Use a comma also before the concluding conjunction in a complex series of phrases: The main points to consider are whether the athletes are skillful enough to compete, whether they have the stamina to endure the training, and whether they have the proper mental attitude.

Most British and Australian style guides also discourage use of the serial comma in simple lists, allowing it only "when its omission might either give rise to ambiguity or cause the last word or phrase to be construed with a preposition in the preceding phrase" (Australian Government's Style Manual for Authors, Editors and Printers).
 

Should You Use the Oxford Comma?

What's our advice? Unless you're writing for an American newspaper, living in the U.K. or Australia, or leading a campaign against superfluous punctuation, use the serial comma, the Harvard comma, or the Oxford comma. "It gives starch to the prose," says Mary Norris, "and can be very effective.

If a sentence were a picket fence, the serial commas would be posts at regular intervals."

* Mary Norris, "Holy Writ." The New Yorker, February 23 and March 2, 2015.