Last Christmas I bought my daughter Claire an entertaining book on grammar called Eats, Shoots and Leaves. The name is derived from the following joke about poor punctuation:

The point of the joke is that comma placement matters.

On to the Oxford comma . . .

The Oxford comma is the last comma in a series of items in a list before a conjunction, usually “and” and sometimes “or.” It is also called the “serial comma.” In the phrase “red, white, and blue” the comma after “white” and before “and” is an Oxford comma.

People tend to fall within one of three camps with respect to the Oxford comma:

1. Oxford comma lovers – Oxford commas are necessary for clarity
2. Oxford comma haters – Oxford commas are snobby, highbrow and unnecessary
3. What’s an Oxford comma and/or who cares? (See Vampire Weekend video below for an expression of this camp)

Is use of an Oxford comma required? Style manuals aren’t in agreement: Strunk & White’s Elements of Style and The Chicago Manual of Style both dictate the use of an Oxford Comma while the AP Stylebook guides writers to omit it unless doing so would lead to misinterpretation or confusion.

Newspapers, which follow AP style, do not use Oxford commas (unless required to avoid confusion). Many magazines also follow AP style. However, other periodicals such as The Atlantic and The New Yorker use the Oxford comma, as do many book publishers.

Usually, whether or not an Oxford Comma is used is a matter of style and not of material importance. For example, the two sentences below read the same even though one has an oxford comma and one doesn’t.

Other times, use of an Oxford Comma will make a sentence flow better, avoid ambiguity and save the reader from having to stop and figure out the meaning. Consider the following sentences which are often used as an entertaining example of how an Oxford comma can change the potential interpretation of sentence:

We invited the strippers, JFK and Stalin.

vs.

We invited the strippers, JFK, and Stalin.

With the first sentence you may need to stop and think “are JFK and Stalin strippers?” With the second sentence it is clear, without having to stop and think, that strippers were invited along with JFK and Stalin.

Another famous example along this line is this apocryphal book dedication:

I’d like to thank my parents, Ayn Rand and God.

Without an Oxford comma a reader might conclude that the author’s parents were Ayn Rand and God (that would be an interesting household in which to be raised given that Ayn was an atheist).

In both the stripper and Ayn Rand examples the reader can quickly figure out the correct meaning without an Oxford comma. However, by including one the meaning is more clear.

Sometimes an Oxford comma is clearly necessary to avoid ambiguity. A recent lawsuit involving Maine dairy delivery drivers provides an apt example. The drivers sued their employer claiming that they were owed overtime pay. The employer claimed the drivers were not eligible for overtime due to state statute. The statute provided that jobs ineligible for overtime were those involved in “the canning, processing, preserving, freezing, drying, marketing, storing, packing for shipment or distribution of: (1) Agricultural produce; (2) Meat and fish products; and (3) Perishable foods.”

The issue was how to interpret highlighted language: does it refer to one job or two? Should you read “packing for shipment or distribution” is a single job (i.e. being a “packer”) or is “packing for shipment” one job and “distribution” a separate job? There is a big difference in those two interpretations because while the drivers were distributors of dairy they were not packers. The parties ended up settling for $5 million, which was half of the damages claimed by the drivers.

Before we all jump on the Oxford comma bandwagon (if you weren’t there already), consider that the Oxford comma can also create ambiguity. Using examples similar to the above:

We invited the stripper, JFK, and Stalin.

I’d like to thank my mother, Ayn Rand, and God.

In these cases, use of the Oxford comma creates ambiguity because the reader has to infer whether the commas around JFK and Ayn Rand are denoting an appositive or separating items in a list. An appositive is a word or phrase that refers to the same thing as another noun in a sentence. “My wife, Tammy” is an example of a nonessential appositive because “my wife” and “Tammy” refer to the same person. Above, offsetting “JFK” with commas would define the stripper as JFK if it were an appositive. Same thing for the Ayn Rand example – offsetting with commas might be defining her as “my mother.”

Of course, with all these examples the reader can figure out the meaning, but including or omitting an Oxford comma can make the sentence read more clearly without the risk of confusion. Be on the lookout for situations like the Maine dairy case – sometimes use (or not) of an Oxford comma is essential.

At the end of the day, whether to use an Oxford comma is mainly a matter of style. The primary advice from experts is be consistent within documents – don’t flip back and forth in Oxford comma usage except when context dictates you must deviate from your chosen Oxford comma style.

Here’s a great song by Vampire Weekend about the Oxford comma that appropriately begins with the line “Who gives a fuck about an Oxford comma?” (It may seem strange that an indie rock band would have a song about grammar, but they are a pretty brainy band: the band members met while attending Columbia University.)