Learn When to Be Restrictive

Do you find the rules regarding comma usage restrictive? Or just confusing?

Some comma confusion comes from understanding restrictive and nonrestrictive elements. Often these elements are relative clauses, which sometimes begin with wh words such as which, when, where or who. (The previous sentence is an example of a nonrestrictive clause)

The key to choosing whether or not to set off an element with a comma or pair of commas has to do with the nature of the element.

Is the word, phrase, or clause in question essential to the meaning of the sentence? If so, it’s a restrictive element, and there’s no comma needed.

Nonrestrictive elements provide additional but nonessential information. They take commas.

Take a look at this sentence:

  • The cookies [that are] on the bottom shelf are sugar-free.

That are on the bottom shelf is essential information. You want to differentiate these cookies from ones located somewhere else. In this next sentence, the location of the cookies is nonessential. It implies (perhaps) that there are no other cookies around:

  • The cookies, which are on the bottom shelf, are sugar-free.

Look at the difference in meaning and emphasis between these pairs of sentences:

  • The car [that] Jane bought is brand-new.
  • The car, which Jane bought, is brand-new.

That Jane bought is a restrictive clause because it provides essential information. The reader needs to know which car is being discussed—the one Jane bought. In the second sentence, the only essential information is that the car is new. The writer implies that who bought it doesn’t matter or isn’t the important point. You can take that middle phrase out and the important information is still there.

How about these?:

  • The neighbors who live across the street answered my call for help.
  • The neighbors, who live across the street, answered my call for help.

Setting who live across the street in commas makes that information additional but not essential. In the first sentence it’s important to note which neighbors helped. In the second sentence, it’s not essential to know they live across the street.

If you can take out the phrase set within the commas and your intent is still clear, that phrase is nonessential and your commas are correct. If not, you know what to do with those commas.

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  1. Commas remove ambiguity among other things. I spend quite a bit of time thinking of restrictive clause principles and the rest making sure my sentences are not ambiguous.

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