Over the holiday season when talk turns to commas, invariably someone asks about commas in a series. “How about that comma before the conjunction—you know when there are three or more words in a series?” someone will ask. “Do we still include it? What’s the rule about that?”
Those folks are referring to the “serial comma,” also known as the Oxford Comma or the Harvard Comma, not because it is a more academic comma, but because it is used by Oxford University Press and Harvard University Press, as well as many other publications. The serial comma is used more commonly in the United States and less commonly, in Britain, ironically, being known as the Oxford comma.
The serial comma is placed before a conjunction, such as and, or, and nor and sets off the conjunction and the last item in the series from the rest of the items.
“Items” can be words, phrases, or clauses:
Sara would like potatoes, carrots, and beans with her turkey. [nouns]
The beautifully-decorated, sparking, dining-room table was a sight to see. [adjectives]
The family will set the table, eat dinner, and have dessert before their favorite television show comes on. [verbs]
Over the meadow, past the church, and through the woods to grandmother’s house we go. [prepositional phrases]
Why do we use the serial comma? Many times, it is to make meaning clear.
At the movies I saw two friends, my dance partner and a neighbor. Without the comma it is unclear if the friends were the dance partner and a neighbor or if the speaker saw four people: two friends, her dance partner, and a neighbor.
At the movies I saw two friends, my dance partner, and a neighbor. With the comma added, it is clearer that the speaker saw four different people.
The serial comma is required by many style manuals, and even though not always mandatory, it is easier and more effective to be consistent, especially when teaching our students.
There is one exception to the serial comma—when an item or items in the series contain commas, use a semicolon between the items.
At dinner I was introduced to Martha, my mother’s best friend; Frank, a distant cousin; and a neighbor of the hostess.