Adjective Clauses - 13

Using Adjective Clauses - 13. Avoid these Mistakes - Part 4

We have seen that you should be careful about several possible types of errors with adjective clauses. Here are two more things to avoid:


1. Be careful with punctuation. Do not use commas with restrictive adjective clauses.

Some adjective clauses give information which is necessary in specifically identifying nouns. These clauses are restrictive. Other adjective clauses give information which provides extra information, but which is not necessary in specifically identifying nouns. These clauses are nonrestrictive.

Use commas with nonrestrictive adjective clauses. Do not use commas with restrictive adjective clauses.

Examples
Incorrect: Do you know the *pages, which we're supposed to read tonight?
The adjective clause is needed to show which pages are being talked about. A comma should not be used.
Correct: Do you know the pages which we're supposed to read tonight?

Incorrect: Joe has a *watch, which once belonged to his grandfather.
The adjective clause is needed to show which watch is being talked about. A comma should not be used.
Correct: Joe has a watch which once belonged to his grandfather.

Incorrect: Dr. *Jordan who teaches my physics class was born in Germany.
The adjective clause is not needed to show which person is being talked about because the name makes this clear. Two commas should be used.
Correct: Dr. Schnabel, who teaches my physics class, was born in Germany.

Incorrect: John's *mother who is a nurse is named Sandra.
Because John has only one mother, the information is extra. Here, a comma should be used.



Correct: John's wife, who is a nurse, is named Gloria.

Correct: Bob's sister who is a nurse is named Angie.
If Bob has more than one sister, this sentence is correct.
Correct: Bob's sister, who is a nurse, is named Angie.
If Bob has only one sister, this sentence is correct.

2. Do not use that in nonrestrictive adjective clauses. Instead, use which.

In restrictive adjective clauses, both that and who can be used to refer to people, and both that and which can be used to refer to things. This is not true for nonrestrictive adjective clauses, however: that cannot be used. Instead, use who or which.

Examples

Correct: The professor who teaches my physics class was born in Russia.



Correct: The professor that teaches my physics class was born in Russia.
Incorrect: Dr. John, that teaches my physics class, was born in Russia.
Correct: Dr. John, who teaches my physics class, was born in Russia.

Gerunds are verbs which are used as nouns. (right)
Gerunds are verbs that are used as nouns. (right)
Gerunds, that are verbs which are used as nouns, end in -ing. (wrong)
Gerunds, that are verbs that are used as nouns, end in -ing. (wrong)
Gerunds, which are verbs that are used as nouns, end in -ing. (right)
Gerunds, which are verbs which are used as nouns, end in -ing. (right)

Note: The second which in the sentence above is correct but awkward; for variety, that should be used instead.