Definition: A non-defining relative clause (also called non-identifying relative clauses or non-restrictive relative clauses) provide interesting ADDITIONAL information which is not essential to understanding the meaning of the sentence. It tells us more about someone or something, but do not define it.
* Elephants that love mice are very unusual.
* This tells us which elephants we are talking about.
* Elephants, which are large and grey, can sometimes be found in zoos.
* This gives us some extra information about elephants – we are talking about all elephants, not just one type or group.
* My sister, who lives in France, is coming to stay with me next week.
* “who lives in France” is not essential, which means that I only have one sister and she does not need to be defined by the “relative clause”)
Punctuation Correct punctuation is essential in non-defining relative clauses. If the non-defining relative clause occurs in the middle of a sentence, a comma is put before the relative pronoun and at the end of the clause. If the non-defining relative clause occurs at the end of a sentence, a comma is put before the relative pronoun.
* My friend John, who went to the same school as me, has just written a best-selling novel.
Relative pronouns The following relative pronouns are used in non-defining clauses:
Person Thing Place
Subject who which
Object who/whom which where
In non-defining clauses, you cannot use “that” instead of “who”, “whom” or “which”.
You cannot leave out the relative pronoun, even when it is the object of the verb in the relative clause:
* He gave me the letter, which was in a blue envelope.
* He gave me the letter, which I read immediately.
Non-defining clauses can be introduced by expressions like “all of”, “many of” + relative pronoun:
all of + whom + which
any of + whom + which
few of +whom + which
both of + whom + which
each of + whom + which
either of + whom + which
half of + whom + which
many of + whom + which
most of + whom + which
much of + whom + which
none of + whom + which
one of + whom + which
two of etc… + whom + which
* There were a lot of people at the party, many of whom I had known for years.
* He was carrying his belongings, many of which were broken.
The relative pronoun “which” at the beginning of a non-defining relative clause, can refer to all the information contained in the previous part of the sentence, rather than to just one word.
* Chris did really well in his exams, which was a big surprise.
* = the fact that he did well in his exams was a big surprise.
* An elephant and a mouse fell in love, which is most unusual.
* = the fact that they fell in love is unusual).
* Mrs. Jackson, who is very intelligent, lives on the corner.
* We stopped at the museum, which we’d never been into.
* I’ve just met Susan, whose husband works in London.
* I spoke to Fred, who explained the problem.