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