Relative clauses

Subject of the verb of the relative clause (cannot be omitted)		Object of the verb of the relative clause (can be omitted)	Possession (cannot be omitted)
used for people	who/that	who/whom/that	whose
used for people	There's the boy who/that started the fight.	Here's the woman (who/that) I told you about last week.	This is Mrs Smith, whose daughter works in my office.
used for things/animals	which/that	which/that	whose/of which
used for things/animals	I saw a film which/that was very good.	This is the book (which/that) I read last week.	This is the house whose roof/the roof of which was destroyed.
What can be used as subject or object or to emphasize a word or phrase. He didn't do what I told him. That can be used instead of who, whom or which but is never used after commas or prepositions. He's the man who/that gave me your address. That hotel, which (not that) is by the sea, is where we stayed. That usually follows superlatives and words such as: something, nothing, anything, all, none, many and few. There's nothing that he can't do.