Read the following sentence:

I don’t know what she wants.

The sentence given above has two parts:

1.    I don’t know
2.    What she wants

Each one of them is part of a larger sentence and has a subject and a predicate of its own. Each part is, therefore, a clause. A clause is the smallest form of a sentence. Having a basic knowledge of clauses is essential to express our thoughts in various sentence structures.

In the sentence given above the clause ‘I don’t know’ makes good sense and hence may stand by itself as a complete sentence. It is, therefore, called the principal or main clause.

Now consider the second clause ‘what she wants’. This clause also has a subject and a predicate of its own but it doesn’t make complete sense and hence cannot stand by itself. It is, therefore, called a subordinate or dependent clause.

Subordinate clauses

There are three kinds of subordinate clauses: the adjective clause, the adverb clause and the noun clause.

The adjective clause

A subordinate clause which serves as an adjective is called an adjective clause.

I have lost the book which he gave me.

Here the clause ‘which he gave me’ says something about the noun book. It is, therefore, used as an adjective. A subordinate clause which does the work of an adjective is an adjective clause.

The woman, whom you are talking about, is my boss.

Here the subordinate clause ‘whom you are talking about’ says something about the noun woman. It is, therefore, used as an adjective.

He is the boy who won the first prize.

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

Adverb clause

A subordinate clause which serves as an adverb is called an adverb clause. We have seen that an adverb modifies a verb, an adjective or another adverb. Similarly, an adverb clause is also used to modify a verb, an adjective or an adverb.

I like John because he is honest.

Here the subordinate clause ‘because he is honest’ modifies the verb like. It says why I like John. It is, therefore, an adverb clause of reason or cause.

We must get the roof repaired before the rains set in.

Here the subordinate clause ‘before the rains set in’ modifies the verb get repaired. It says when we should get the roof repaired. It is, therefore, an adverb clause of time.

Noun clause

A subordinate clause which does the work of a noun is called a noun clause.

I don’t know what she wants.

Here the subordinate clause ‘what she wants’ is the object of the verb know.

We have seen that only nouns or noun equivalents can be used as the subject and the object of a verb. The clause ‘what she wants’, therefore, does the work of a noun and hence is called a noun clause.