Many lawyers seem to think that commas are theirs to do with as they please. Not so. There are actually rules on when and how commas should be used — and not used. Here are some of the most common uses for the comma.

Set off an introductory clause:

While washing the dishes, I scalded my hand.

The comma is not optional in the sentence above. However, if the introductory clause is quite short, some style manuals allow for omitting it, as in:

After dinner I washed the dishes.

Set off a parenthetical:

My Labrador retriever, which was named Duke, was my constant companion.

His wife, Jane, made a spectacular dinner.

She wore her favorite dress, which was yellow.

Without the commas, the meanings of the above sentences are obscured a little. It would seem as if Duke is but one of several Labradors owned by the speaker, a man has more than one wife, and a girl possesses multiple yellow dresses. A parenthetical is a clause, word, or phrase that is not essential for sentence to make sense. If you can omit a phrase and the sentence reads fine, then it should be set off with commas. Hint: The word “which” in the middle of a sentence usually indicates that a comma is needed. If “which” begins a phrase that isn’t a parenthetical, then it should probably be changed to “that.”

Separate three or more elements in a series:

Wedding rings are made from gold, platinum, and titanium.

One must either drive within the speed limit, pay fines, or get a good radar detector.

Some style manuals allow for omission of the comma immediately preceding the conjunction. I’m against this, because it sometimes leads to ambiguities.

Join two or more independent clauses — conjunction required:

Elaine and Puddy broke up with each other, but they kept getting back together.

Elaine’s father was a famous author, and Elaine worked as an editor for a publishing company.

It’s important to note here that, without that all-important conjunction, the sentences above would be comma-spliced. This is a common error, and one I see in published books all the time. But that doesn’t make it a good idea.

Set off the year in a date that appears in a sentence:

February 12, 1809, was Lincoln’s date of birth.

That second comma gets left out as often as not; I wince a little every time I see that error.

Set off most titles and designations that appear in a name:

James Weintraub, Esq., opened the conference with a speech about antiquated, meaningless, and pretentious titles used by lawyers.

He represented Vandelay Industries, Inc., in its suit against Kramerica Industries.

As with the preceding example, everyone “gets” the first comma; it’s the second one they can’t seem to wrap their heads around. Try thinking of the title or designation as a kind of mini-parenthetical. The sentence would read fine without it, and so it should be set off with commas — not just preceded by one.

Further reading on commas:

Prof. Brians’s “Commas” essay at his Common Errors site

Purdue Writing Lab: “Using Commas”

The Blue Book of Grammar and Punctuation: Commas