Punctuation

Commas with adjective clauses

Adjective clauses begin with a relative pronoun (who, whom, whose, which, that) or with a relative adverb (where, when). They contain a subject and a verb but they cannot stand alone—they modify a noun or pronoun in the sentence. They always follow the word they modify, usually immediately.

Adjective clauses are either restrictive or nonrestrictive. Nonrestrictive adjective clauses are set off with commas; restrictive adjective clauses are not.

Heading: Nonrestrictive clause (with commas). Example sentence with editing. Original sentence: Ed's house which was located on thirteen acres was furnished with bats in the rafters and mice in the kitchen. Revised sentence: Ed's house, which was located on thirteen acres, was furnished with bats in the rafters and mice in the kitchen.

The clause which is located on thirteen acres does not add essential information about the identity of the house, so the clause should be set off with commas.

Heading: Nonrestrictive clause (with commas). Example sentence with editing. Original sentence: William Shakespeare whose credibility has been questioned in recent years wrote nearly forty plays. Revised sentence: William Shakespeare, whose credibility has been questioned in recent years, wrote nearly forty plays.

There is only one Shakespeare, so the modifier cannot restrict the meaning. Use commas here to set off non-essential information.

Heading: Restrictive clause (no commas). Example sentence with editing. Original sentence: Ramona's cat that just had kittens became defensive around the other cats in the house. Revised sentence: Ramona's cat, that just had kittens, became defensive around the other cats in the house.

Ramona has more than one cat. Because the adjective clause that just had kittens identifies the particular cat, the information is essential (no commas).

Heading: Restrictive clause (no commas). Example sentence with editing. Original sentence: The Oklahoma representative, who voted against the health care bill, received dozens of phone calls from his constituents. Revised sentence: The Oklahoma representative who voted against the health care bill received dozens of phone calls from his constituents.

There are several representatives from Oklahoma; the adjective clause who voted against the health care bill identifies the specific representative. It is therefore essential to the meaning of the sentence and is not set off with commas.

NOTE:Use that only with restrictive clauses. Many writers prefer to use which only with nonrestrictive clauses, but usage varies.

Exercises:

Major uses of the comma 1

Major uses of the comma 2

All uses of the comma