Examine the groups of italicized words in the following sentences.
I expect to get the first prize. (Expect what?)
I expect that I will get the first prize. (Expect what?)
Here the first group of words ‘to get the first prize’ makes sense, but not complete sense. It does not have a subject or predicate of its own. It is therefore a phrase. And because this phrase is the object of the verb expect it does the work of a noun. In other words it is a noun phrase.
Now consider the second group of words ‘that I will get the first prize’. It has a subject and a predicate of its own. It is therefore a clause. And because it is the object of the verb expect, it does the work of a noun. Therefore we call it a noun clause.
Now study the following sentence.
That she should forget me so quickly was rather a shock.
Here the noun clause ‘that she should forget me so quickly’ is the subject of the verb was.
More examples of noun clauses are given below:
She asked me what I was doing. (Object of the verb asked)
He said that he would not come. (Object of the verb said)
No one knows who he is. (Object of the verb knows)
That you should say this is rather strange. (Subject of the verb is)
I don’t know what he wants. (Object of the verb know)