The Relative Pronouns are who, with its possessive whose and objective whom; which, with its possessive whose (or of which); what, that, as, and but. 

Who and whom are used of persons; whose is used of persons or things; which is used of things or non-human creatures. That can be used of things or persons. 

E.g.:

The boy who is standing over there is my classmate. 

The boy whom you were speaking to is like you.

Take what you want. 

The boy whose coat is torn looks poor. 

The letter, which you gave me to post, required a two anna stamp.

The station to which we are going is Anuradhapura. 

That is the boy that I saw playing marbles.

As when a relative pronoun is used in the following ways:

1. With such and same. 

E.g.:

It was such a sight as I never want to see again.

He is the same kind of man as my father. 

2. In expressions like: Common names, as Smith and Jones. (Here as = which may be.)

3. In the sense of a fact which:

E.g.:

He was a Chinese-man, as we could tell by his talk

But when a relative pronoun is used thus:

E.g.:

There was not a man or woman there but wept. (In this case but = who did not.) .

The noun or pronoun to which a relative pronoun refers is called the antecedent. 

The Relative pronoun must agree in gender, number and person with the noun to which it refers the antecedent. But, it is not always of the same case as the antecedent.

E.g.:

This is the boy who helped me.

This is the boy of whom I spoke to you.

Tell me what you would like to do. 

Here are the books which I borrowed for you.

Here are the books in which you will find the information you are needing.   

Relative Adjectives.

Relative Adjectives are which and what.

E.g.:

I don’t know which way I have to go.

Please tell me what time it is.

Compound Relative Pronouns.

Whoever, whichever and whatever are not only interrogative, but also Compound Relative Pronouns. In this case, too, the ending -ever emphasizes the pronouns who, which and what.

E.g.:

Whatever it may be, I cannot see him today. 

They accused whomever they liked of treason.

Whosesoever it is I shall keep it myself.

You may have whichever you please.

Whatever you do, don’t forget to be polite.

I know nothing whatever of him.

Compound Relative Adjectives.

Whichever (whichsoever) and whatever (whatsoever) are also used as Compound Relative Adjectives.

E.g.:

Whichever (or whichsoever) road you take, you will find your way home.

Money, in whatever hands, will give power.

In whatever place man may be, the spring will come to him.

(In these two sentences whatsoever may be used instead of whatever.)

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