You will notice in these sentences we have expressed practically the same thought as in the sentences where the noun clause was used as the subject of the verb.

But now we have this little pronoun it used as the subject, instead of the clause, which is the real subject of the sentence. It is simply used as the introductory word in the sentence. The noun clause is in reality the subject of the sentence.

365. Noun clauses may also be used as the predicate complement with a copulative verb. For example:

In all of these sentences the noun clause is used as the complement of the incomplete verbs is and was, to complete the meaning, just as we use a noun as the predicate complement of a copulative verb in such sentences as, Socialism is a science. War is murder.

366. A noun clause may also be used in apposition to a noun to explain its meaning. Apposition means to place alongside of. Note in the following sentences:

In the first sentence, the clause, that such a law had been passed, is placed beside the noun fact and explains what that fact is. The clause, that the matter should be laid on the table, is in apposition to and explains the noun motion.

These noun clauses are used in apposition.

Exercise 3