SOCC Writing Center

Comma Use With Restrictive/Non-restrictive Words

Put commas around non-essential or non-restrictive expansion words that appear with nouns. These expansion words provide information that can be left out without changing the basic sense of the sentence.

Example: Alzheimer’s disease, a progressive impairment of the brain, strikes many older Americans each year.

By non-restrictive, we mean that the expansion words are not necessary; they, thus are part of the noun phrase. Usually, you can “hear” words that interrupt the flow of thought in a sentence. However, when you are not sure if certain words are interrupters, remove them from the sentence. If it still makes sense without the words, you know the words are interrupters and that the information they give is non-essential. Such non-essential or non-restrictive information is set off with commas.

Example: Susie Hall, who is my best friend, won a new car.

The words who is my best friend are extra information, not needed to identify the subject of the sentence, Susie Hall. On the other hand, in the sentence

Example: The woman who is my best friend won a new car.

The expansion words who is my best friend supply essential information needed for us to identify the woman. If the words were removed from the sentence, we would no longer know which woman won the sweepstakes. Commas are not used around such essential or restrictive information.

THAT/WHICH

Example: He is wearing the cape that I am looking for. (“that I am looking for” expands “cape,” and it is restrictive, defining which cape I am referring to.

When an expansion phrase or clause begins with “which,” it is non-restrictive.

Example: It is the third movie of the year, which is the last of the season. (“which . . .” simply adds information, not defining which movie is being referred to.

APPOSITIVES

An appositive is a noun or noun phrase that repeats the basic essence of a noun, using different terms. An appositive can be either or non-restrictive .

First Names. An exception to the rule of restrictive/non-restrictive is the mention of a first name as an appositive. In all such cases, the commas are left out, whether restrictive or not.

Example. My sister Marsha likes to swim.
The salesman Dave is offering a great deal.

Dates and States. In a date, the year is inserted with commas just as a non-restrictive appositive. In a mention of city/state, the state is inserted with commas in the same way.

Example: The weather on March 16, 1996 , was sunny.
We love Coos Bay, Oregon , because of the weather.