who subject or object pronoun for people I told you about the woman who lives next door.
which subject or object pronoun for animals and things Do you see the cat which is lying on the roof?
which referring to a whole sentence He couldn’t read which surprised me.
whose possession for people animals and things Do you know the boy whose mother is a nurse?
whom object pronoun for people, especially in non-defining relative clauses (in defining relative clauses we colloquially prefer who) I was invited by the professor whom I met at the conference.
that subject or object pronoun for people, animals and things in defining relative clauses (who or which are also possible) I don’t like the table that stands in the kitchen.