Relative clauses are often used to tell you which person or thing the speaker is talking about. However some relative clauses are used to give further information about the person or thing
Examples:
The old car, which has been sitting out in the road for weeks, has been taken away by the Council. (The old car explains which car, and then the following two clauses give further information about it.)
My brother, who works in Singapore, is getting married.
Which and Who
n relative clauses which give extra information, it is necessary to use who for people and which for things; You cannot use that nor can you leave out who or which. With these clauses it is also necessary to put commas at the beginning and at the end of the clauses.
Examples:
The Ryanair plane, which we took from Girona, had to land in Chambery for an engine problem.
The pediatric nurse, who sometimes works the same shift as me, is moving to Spain.
Whose, Where and Whom
Whose, where and whom can also be used in relative clauses which give further information.
Examples:
The psychiatrist , whose father works with John, is coming to stay next weekend.
My boss, whom you once sat next to at a company dinner, is going to be at this meeting.
Prepositions
In relative clauses which give further information, one can put prepositions before whom or which, although this is more common in written text than in speech, where often the preposition is kept after the verb and who is used instead of whom.
Examples:
Mrs Elbow, to whom I had spoken on the telephone, had sent me the documents that I needed.
Mrs Elbow, who I had spoken to on the telephone, had sent sent me the documents that I needed.
We visited parts of Miami to which I had never been before.
We visited parts of Miami, which I had never been to before.
All Of and Most Of
The following words can be used with whom or which:
none of, many of, much of, a few of, some of, any of, half of, each of, both of, neither of, one of etc.
Examples:
We tried three chemists, none of which had the right medicine.
He has made many friends at work, many of whom live in the same part of London.
Two children, neither of whom I knew, knocked on my door and asked if I could help them.