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Opinion

A Word, Please: When do we use commas to set off information?

Oxford English Dictionary
Commas set off nonrestrictive matter, but they’re not used around restrictive information.
(Oxford University Press)

“A Bay Area real estate heiress whose family posted $35-million bail to keep her out of jail until her trial was acquitted Friday of killing the father of her children.”

That’s the nut of a story published recently by the Los Angeles Times that raised a question in a reader’s mind: Should there be commas after “heiress” and “jail,” wondered Carol in Southern California?

As is the case for so many questions that land in my in-box, I can’t offer a clear yes or no answer. But I can present an argument about why I believe the answer is no.

The reason lies in the concepts of restrictive and nonrestrictive information.

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Commas set off nonrestrictive matter, but they’re not used around restrictive stuff.

To see the difference, compare these two sentences: The man who stole my purse was wearing a baseball cap. The man, who stole my purse, was wearing a baseball cap.

In most but not all situations, the second one would be wrong. Why? Because we can be pretty sure that “who stole my purse” is intended as information that identifies which man you’re talking about.

That clause restricts the scope of the subject, helping the reader better figure out which man is “the man” in question. So the information about purse-stealing is crucial to understanding which man is being discussed.

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As a rule, if you lift restrictive information out of a sentence, you lose specificity of one of the nouns in the sentence. So take out the stuff about purse-snatching and you get: “The man was wearing a baseball cap.”

Chances are the reader now has a less-clear idea what man you’re talking about.

There’s a chance that’s not true. If the context has already supplied the needed specificity, then it’s possible “the man was wearing a baseball cap” is all the detail you need.

For example, imagine that the longer passage was: “A man mugged me. He grabbed my purse and ran. The man was wearing a baseball cap.”

Here, the first two sentences introduce the idea of “the man.” By the time we reach the third sentence, we know who she’s talking about. So “the man” is no less specific than “the man who stole my purse.”

Let’s apply these ideas to our sentence about the heiress. Do we believe The Times used that bit about the $35-million bail to help the reader identify the subject, the heiress?

I think they did because I think they wanted to be more specific than “A Bay Area real estate heiress was acquitted.” Newspapers don’t usually take that approach. They aim for specificity and to be as complete as possible in the information they supply.

So I believe they were talking not about an heiress but about an heiress out on $35-million bail.

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I could be wrong.

Either way, this gives you the basis for making up your own mind about those commas. If you think the information is restrictive, adding specificity to “heiress,” the rule says no commas.

If you think the bail business can be lifted out of the sentence with no loss of clarity about which heiress we’re talking about, then it’s nonrestrictive information that should be set off with commas.

The same idea governs a style rule about “that” and “which.” Both Associated Press and Chicago editing styles say that restrictive clauses take “that” and nonrestrictive clauses take “which.” Those “which” clauses are set off with commas.

The car that I buy will need to have good gas mileage. The car, which is red, gets good gas mileage.

In the first, the reader has no idea which car is “the car” unless you keep in the “that” clause. In the second, it’s safe to assume that the reader already knows which car is “the car,” so the clause pointing out that it’s red doesn’t help the reader narrow that down.

In some cases, you can decide whether you mean the added information to be restrictive or not. But either way, that should serve as the basis for whether you include those commas.

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