Relative Pronouns

A relative pronoun links a main clause to a subordinate clause:

 
It is the book       which    I bought
Main clause.                     Subordinate clause

The relative pronouns   are: Who, Whom, That, Which and Whose
1. Some examples:
I meet a person whom I saw last year.
I find a pair of jeans, which I lost yesterday.
Did you find the key (that) that you wanted?
Do you know the man that she is talking to?
The hotel whose price is beyond $200 a night is not affordable for her.

2. Who and Whom
WHO
Who is the subject pronoun, 
whom is the object pronoun. 

WHO is the relative subject pronoun for people.
WHOM relative object pronouns for people.

Who and whom are used:
 - In questions:
Who called? 
- He called
To whom did she speak? 
- She spoke to her father. 

- Or in relative clauses: 
The man who writes this book is unknown.
He called the professor, with whom he had 
attended many meetings.

Whom
 
Use whom with prepositions: 
She liked his friend Bill, for whom she had voted in several elections. 
("She had voted for [whom] her in several elections.") 

To whom did you send this letter? 
("You sent the letter to [whom] him.") 

Whom did they see? ("They saw [whom] us.") 
 
3.Which, That and Whose:
WHICH is the relative pronoun for things.
THAT: is used for who and which
WHOSE: is a possessive relative pronoun.

She is the woman that I saw at the office.

The relative pronoun can be omitted when it is followed by a subject
She is the woman I saw at the office.

The relative pronoun can’t be omitted: it isn’t followed by a subject
He was the only one that knows how to solve the problem.


When the relative pronoun is preceded by a comma, we can not drop it:
The car, which I bought seven years ago, is still.

Whose can’t be omitted:
He saw the friend whose father was died.

3. Summary: Relative clauses
-We always need     Which, That, Who   in the case of the subject
-Who for people
-Which for things
-That for both (mainly for things)
-We don't need     Which, That, Who   in the case of the object.
-WE can use where in the case of the place.