A noun clause functions as a noun. It can be the subject or object of a verb. A noun clause is a subordinate clause. That means it cannot stand alone.

Study the following sentences.

I don’t believe your story. (Here the noun story is the object of the verb believe.)
I don’t believe what you said. (Here the clause what you said is the object of the verb believe. We have already learned that only nouns can be the subject or object of a verb. A clause that does the work of a noun is therefore a noun clause.)

Now study the pair of sentences given below.

His remarks were objectionable. (Here the noun remarks is the subject of the verb were.)
What he said was objectionable. (Here the clause what he said is the subject of the verb was. A clause that serves as the subject or object of a verb is always a noun clause.)

A noun clause can also be the object of a preposition.

I’m not interested in what she is doing. (Here the noun clause what she is doing is the object of the preposition in.)
Noun Clauses as Compliments

A noun clause can act as a subject complement. A subject complement says something about the subject. A subject complement is not the same as an object. Instead it is an expression that defines or describes the subject.

Susie is an architect. (Here the noun an architect is not the object of the verb is. It is the complement of the subject Susie.)

The most important verbs that are usually followed by subject complements are: is, am, are, was and were.

We have already seen that noun clauses can act like subject complements.

John’s problem is that he doesn’t have a job. (Here the clause that he doesn’t have a job is the complement of the subject John’s problem.)