A noun clause does the work of a noun. We have seen that a noun serves five purposes, so does a noun clause. Given below are pairs of sentences having similar meanings. One of each pair is constructed with a noun. The other is constructed with a noun clause.

As the subject of a verb

The story was true. (Here the noun story serves as the subject of the verb was.)
What he said was true. (Here the clause ‘what he said’ serves as the subject of the verb was.)

As the object of a finite verb, participle or infinitive

He told me a story. (Here the noun story is the object of the verb told.)
He told me that he was going. (Here the noun clause ‘that he was going’ is the object of the verb told.)

As the object of a preposition

Pay attention to my story. (Here the noun story is the object of the preposition to.)
Pay attention to what I say. (Here the noun clause ‘what I say’ is the object of the preposition to.)

Subject complement

My brother is a doctor. (Here the noun doctor is the complement of the subject my brother.)
My belief is that he would pass. (Here the noun clause ‘that he would pass’ is the complement of the subject belief.)

In apposition to a noun or pronoun

Alice, my sister, lives abroad. (Here the noun my sister is in apposition to the noun Alice.)
The news that he won made us happy. (Here the noun clause ‘that he won’ is in apposition to the noun news.)

How to construct a sentence having a noun clause

Making a sentence having a noun clause is very simple. One of the ways is to begin a sentence like this:

He says that…

Whatever clause you put after ‘that’ will automatically become a noun clause.

He says that he is not interested in the offer. (Noun clause – that he is not interested in the offer.)

Instead of say you can use any of the following verbs:

Know, believe, think, realize, feel, hope, wish, understand, see, notice, find, discover, hear, listen, say, tell, ask, request, order, explain, suggest etc.

He suggested that I should consult a doctor. (Noun clause – that I should consult a doctor)
I think that he is a traitor. (Noun clause – that he is a traitor)
I discovered that he was cheating me. (Noun clause – that he was cheating me)
I heard that he had won the match. (Noun clause – that he had won the match)