The serial comma, also known as the Oxford comma or the Harvard comma (because the Oxford and Harvard University Press style guides require it), is the final comma before the coordinating conjunction “and” in a list of three or more items. While many presses in addition to Oxford and Harvard favor the serial comma, newspapers have historically omitted it to save space on the printed page. Reflecting this journalistic preference, our own Office of Communications recommends its omission in the case of “print and electronic materials written for and about Princeton University” unless “it aids in comprehension.” Some writers find the serial comma unnecessary or even pretentious, possibly due to a bias against the institutions with which it is associated; however, the serial comma provides clarity when a list could have multiple interpretations, as in the following sentences:
This book is dedicated to my children, Toni Morrison and God.
The country-and-western singer was joined onstage by his two ex-wives, Kris Kristofferson and Waylon Jennings.
These funny sentences are indeed extreme, but the serial comma would go a long way toward clarifying their meaning.
Some argue that context alone will eventually help the reader discern the writer’s intent. H.L. Mencken, in a supplement to The American Language, hints that the use of the serial comma might even be considered un-American. He notes, “The English are rather more careful than we are, and commonly put a comma after the next-to-last member of a series, but otherwise are not too precise to offend a red-blooded American.”
Still, other “red-blooded Americans” argue that while the meaning of a list is often clear without a serial comma, it does not add confusion and using it every time you write a list of three or more things provides consistency. Wilson Follett, in his 1966 Modern American Usage, suggests,“Use the comma between all members of a series, including the last two, on the commonsense ground that to do so will preclude ambiguities and annoyances at negligible cost.” In other words, if you always use a serial comma, you don’t have to wonder whether you really need it. The following sentence, for example, isn’t muddled by the addition:
The basketball player dribbles, shoots and scores.
The basketball player dribbles, shoots, and scores.
Good writers, American or otherwise, aim for clarity. The serial comma can help us achieve this goal.