How to Form Relative Clause

Imagine, a girl is talking to Tom. You want to know who she is and ask a friend whether he knows her. You could say:

A girl is talking to Tom. Do you know the girl?

That sounds rather complicated, doesn't it? It would be easier with a relative clause: you put both pieces of information into one sentence. Start with the most important thing  – you want to know who the girl is.

Do you know the girl …

As your friend cannot know which girl you are talking about, you need to put in the additional information  – the girl is talking to Tom. Use „the girl“ only in the first part of the sentence, in the second part replace it with the relative pronoun (for people, use the relative pronoun „who“). So the final sentence is:

Do you know the girl who is talking to Tom?

Relative Pronouns

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?

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 

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 which	refers to a reason	the reason why we met him