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?
|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.|
You can practise with the following exercises: