The Most Comma Mistakes

By BEN YAGODA - New York Times

Draft is a series about the art and craft of writing.

As I noted in my earlier article, rules and conventions about when to use and not to use commas are legion. But certain errors keep popping up. Here are a few of them.

Identification Crisis
If I’ve seen it once, I’ve seen it a thousand times. I’m referring to a student’s writing a sentence like:
I went to see the movie, “Midnight in Paris” with my friend, Jessie.
Comma after “movie,” comma after “friend” and, sometimes, comma after “Paris” as well. None is correct — unless “Midnight in Paris” is the only movie in the world and Jessie is the writer’s only friend. Otherwise, the punctuation should be:
I went to see the movie “Midnight in Paris” with my friend Jessie.
If that seems wrong or weird or anything short of clearly right, bear with me a minute and take a look at another correct sentence:
I went to see Woody Allen’s latest movie, “Midnight in Paris,” with my oldest friend, Jessie.
You need a comma after “movie” because this and only this is Mr. Allen’s newest movie in theaters, and before “Jessie” because she and only she is the writer’s oldest friend.
The syntactical situation I’m talking about is identifier-name. The basic idea is that if the name (in the above example, “Jessie”) is the only thing in the world described by the identifier (“my oldest friend”), use a comma before the name (and after it as well, unless you’ve come to the end of the sentence). If not, don’t use any commas.
Grammatically, there are various ways of describing what’s going on. One helpful set of terms is essential vs. nonessential. When the identifier makes sense in the sentence by itself, then the name is nonessential and you use a comma before it. Otherwise, no comma. That explains an exception to the only-thing-in-the-world rule: when the words “a,” “an” or “some,” or a number, come before the description or identification of a name, use a comma.
A Bronx plumber, Stanley Ianella, bought the winning lottery ticket.
When an identifier describes a unique person or thing and is preceded by “the” or a possessive, use a comma:
Baseball’s home run leader, Barry Bonds, will be eligible for the Hall of Fame next year.
My son, John, is awesome. (If you have just one son.)
But withhold the comma if not unique:
My son John is awesome. (If you have more than one son.)
The artist David Hockney is a master of color.
The celebrated British artist David Hockney is a master of color.
And even
The gay, bespectacled, celebrated British artist David Hockney is a master of color.
Full piece at The New York Times