Relstive pronouns

Relative Pronouns Level: lower intermediate relative pronoun | use | example | 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. |
Subject Pronoun or Object Pronoun? Level: lower intermediate
Subject and object pronouns cannot be distinguished by their forms - who, which, that are used for subject and object pronouns. You can, however, distinguish them as follows:
If the relative pronoun is followed by a verb, the relative pronoun is a subject pronoun. Subject pronouns must always be used. the apple which is lying on the table
If the relative pronoun is not followed by a verb (but by a noun or pronoun), the relative pronoun is an object pronoun. Object pronouns can be dropped in defining relative clauses, which are then called Contact Clauses. the apple (which) George lay on the table

Relative Adverbs Level: intermediate
A relative adverb can be used instead of a relative pronoun plus preposition. This often makes the sentence easier to understand.
This is the shop in which I bought my bike.
→ This is the shop where I bought my bike. relative adverb | meaning | use | example | when | in/on which | refers to a time expression | the day when we met him | where | in/at which | refers to a place | the place where we met him | why | for