An adjective clause is a subordinate (dependent)` clause used as an adjective. Like single-word adjectives, adjective clauses describe and modify nouns. The following relative pronouns introduce adjective clauses. Whorefers only to persons.
The man is a police officer. He lives next door.
The man who lives next door is a police officer.
Whomis the objective form of who and refers only to persons.
He is one police officer. I respect him very much.
He is one police officer whom I respect very much.
Whichrefers to animals.
Last week someone hit his son’s dog. The dog was only a puppy.
Last week someone hit his son’s dog, which was only a puppy.
refers to things.
The driver ran through a stop sign. The stop sign is on the corner.
The driver ran through a stop sign, which is on the corner.
refers to groups of people (the audience, crowd, class).
Officer Smith often lectures to high school classes. These classes are learning safe driving principles.
Officer Smith often lectures to high school classes, which are learning safe driving principles.
Thatrefers to persons.
The police officers respect him, too. Officer Smith works with them.
The police officers that Officer Smith works with respect him, too.
refers to animals.
He was very happy with the new puppy. I gave him the puppy last night.
He was very happy with the new puppy that I gave him last night.
refers to things.
I also gave his son a book. The book tells about caring for pets.
I also gave his son a book that tells about caring for pets.
Whoseindicates possession and is used for animals.
The first puppy was six weeks old. His coat was really beautiful.
The first puppy, whose coat was really beautiful, was six weeks old.
used for people.
He is a little boy. His love for animals is very strong.
He is a little boy whose love for animals is very strong.
used for groups of peoples.
We should report pet owners. Their animals are mistreated.
We should report pet owners whose animals are mistreated.
used for things.
This dog house is very old. Its roof has holes in it.
This dog house, whose roof has holes in it, is very old.
The subordinators when, where , and why also introduce adjective clauses.
Whenintroduces adjective clauses describing nouns referring to time.
This is time of year. There are good sales now.
This is time of year when there are good sales.
Whereintroduces adjective clauses describing nouns referring to location.
This is the record store. My friend work here.
This is the record store where my friend works.
Whyintroduces adjective clauses that modify words such as reason and explanation, and so on.
My friend didn’t tell me the reason. He quit his job.
My friend didn’t tell me the reason why he quit his job.
NOTE:The subordinators where /when can also introduce adverb clauses.
However, if the where/when clause modifies a verb it is an adverb clause. But if the where/when clause modifies a noun it is an adjective clause.
a. I eat at the restaurant where I work.
b. I eat where I work.
(verb) (adverb clause)
c. My parents called on a day when I was out.
(noun) (adjective clause)
d. They called when I was out.
(Adverb Clause) why?
Necessary versus Unnecessary Adjective/ Relative Clauses
An adjective/relative clause is either necessary /defining to identify the noun it follows, or it is unnecessary/non-defining
Necessary adjective clauses
A necessary (restrictive) adjective clause is needed to identify the noun and to make the meaning of the sentence clear. Look at the following examples.
a. All students who do not study will fail this course.
(Will all students fail the course? No....