A clause which modifies a noun or pronoun in the preceding clause is known as an adjective clause. The adjective clause is introduced by a relative pronoun or relative adverb. It is also called a relative clause.

The relative pronouns most often used to introduce an adjective clause are: who, which, that, whom and whose. The relative adverbs used to introduce an adjective clause are: when, why, how and where.

Study the following example.

This is the house that Jack built.

Here ‘this is the house’ is the main clause. ‘That my father built’ is the adjective clause which modifies the noun ‘house’. ‘That’ is the relative pronoun and ‘house’ is the antecedent.

More examples are given below.

This is the girl who won the first prize.

Here the adjective clause ‘who won the first prize’ modifies the noun girl.

Time which is lost is lost forever.

Here the adjective clause ‘which is lost’ modifies the noun time.

Examples of relative adverbs

This is the house where James was born.

In this sentence ‘this is the house’ is the main clause. ‘Where James is born’ is the adjective clause. It qualifies the noun ‘house’ which is its antecedent. ‘Where’ is the relative adverb which introduces the adjective (relative) clause.

More examples are given below.

This is the reason why she didn’t come.

Here the adjective clause ‘why she didn’t come’ modifies the noun ‘reason’.

I cannot forget the day when we met for the first time.

Here the adjective clause ‘when we met for the first time’ modifies the noun ‘day’.