I have been fighting for years—since 1961, actually, when I sat on the rim of the copy desk at the old Houston Press—against those who wish to eradicate what is sometimes known as the Oxford (or Harvard) Comma. This is the comma that comes before the “and” or “or” in a series of three or more items. For example, The U. S. flag is red, white, and blue. I do not like vodka, rum, cognac, or tequila.
It's known as the Oxford Comma because it was traditionally used by editors at the Oxford University Press. How Harvard nosed itself into the phrase I cannot say. Some people call it the serial comma.
In the United States, the serial comma is standard usage in most non-journalistic writing, but newspaper stylebooks, including the Associated Press, The New York Times, and The Los Angeles Times, mandate its omission. British English usually does without the serial comma, except for some university presses and the recommendation of Fowler’s Modern English Usage.
Stylebooks notwithstanding, the Oxford Comma is often necessary to clarify meaning. For example, in a book dedication the author might write:
To my parents, Zsa Zsa Gabor and Henry Kissinger.
Without the serial comma, it would appear that the author’s parents are Zsa Zsa and Henry, a situation that, while not inconceivable, is probably not what was meant. With the serial comma, we find that the author is dedicating his book to three unrelated entities:
To my parents, Zsa Zsa Gabor, and Henry Kissinger.
Ironically, the inclusion of an Oxford comma can also cause its own ambiguity, as in this dedication:
To my mother, Zsa Zsa Gabor, and Henry Kissinger.
In this case, the comma could indicate an appositive rather than a series, meaning that the author’s mother is Zsa Zsa. The best way around this kind of confusion is probably to rephrase:
To my mother, and to Zsa Zsa Gabor and to Henry Kissinger.
In her inexplicably best-selling book, Eats, Shoots & Leaves, the British journalist Lynne Truss writes:
"There are people who embrace the Oxford comma, and people who don't, and I'll just say this: never get between these people when drink has been taken."
The Bard of Buffalo Bayou can take the Oxford Comma or leave it alone, but mostly he takes it:
McConnell, Cantor, Boehner and Obama
Faced off one day across a great divide.
From right to left, there was a panorama,
The gap between their views was very wide.
The air was tense, and you could feel the drama,
Until, at long last, Boehner upped and cried:
“Wait! Wait! Insert an Oxford Comma,
Or folks might think I'm on Obama’s side!”