The leading thought of a sentence is called the principal clause.

A clause that has the function of a noun, an adjective, or an adverb, is called a subordinate clause.

Select the principal clauses and the subordinate clauses in the following sentences, and state the function of each subordinate clause:—

1.They knew who did it.
2.The book which you gave me, is here.
3.I shall go when he returns.

A clause that has the function of a noun, is called a noun clause; as, He said he knew his lesson. How I shall reach my destination is the question.

A noun clause may be used:—

1.As the object of a verb; as, He knew what I did.
2.As the subject of a verb; as, What course he pursued is seen now.
3.As the object of a preposition; as, My friend annoyed me by what he said.
4.As a predicate nominative; as, The end of it all is (that) he receives his choice.

A clause that has the use or function of an adjective, is called an adjective clause; as, He found the book which he lost.

A clause that has the use or function of an adverb, is called an adverbial clause; as, I shall go where they are. He will destroy it unless we hinder him.

A sentence that consists of one principal clause, and one or more subordinate clauses, is called a complex sentence; as, I have met the person of whom you speak.