Main points

* You use non-defining relative clauses to give extra information about the person or thing you are talking about.

* Non-defining relative clauses must be introduced by a relative pronoun such as `which’, `who’, `whom’, or `whose’.

* A non-defining relative clause comes immediately after a noun and needs a main clause to make a complete sentence.

1 You use non-defining relative clauses to give extra information about the person or thing you are talking about. The information is not needed to identify that person or thing.
Professor Marvin, who was always early, was there already.

`Who was always early’ gives extra information about Professor Marvin. This is a non-defining relative clause, because it is not needed to identify the person you are talking about. We already know that you are talking about Professor Marvin.

Note that in written English, a non-defining relative clause is usually separated from the main clause by a comma, or by two commas.
I went to the cinema with Mary, who I think you met.
British Rail, which has launched an enquiry, said one coach was badly damaged.

2 You always start a non-defining relative clause with a relative pronoun. When you are talking about people, you use `who’. `Who’ can be the subject or object of a non-defining relative clause.
Heath Robinson, who died in 1944, was a graphic artist and cartoonist.
I was in the same group as Janice, who I like a lot.

In formal English, `whom’ is sometimes used instead of `who’ as the object of a non-defining relative clause.
She was engaged to a sailor, whom she had met at Dartmouth.

3 When you are talking about things, you use `which’ as the subject or object of a non-defining relative clause.
I am teaching at the Selly Oak centre, which is just over the road.
He was a man of considerable inherited wealth, which he ultimately spent on his experiments.

WARNING: You do not normally use `that’ in non-defining relative clauses.

4 You can also use a non-defining relative clause beginning with `which’ to say something about the whole situation described in a main clause.
I never met Brando again, which was a pity.
She was a little tense, which was understandable.
Small computers need only small amounts of power, which means that they will run on small batteries.

5 When you are talking about a group of people or things and then want to say something about only some of them, you can use one of the following expressions:

many of which, many of whom, none of which, none of whom, one of which, one of whom, some of which, some of whom

He talked about several very interesting people, some of whom he was still in contact with.

6 You can use `when’ and `where’ in non-defining relative clauses after expressions of time or place.
This happened in 1957, when I was still a baby.
She has just come back from a holiday in Crete, where Alex and I went last year.

Unit 94 Participle clauses
Main points

* Nouns are followed by `-ing’ clauses that say what a person or thing is doing.

* Nouns are followed by `-ed’ clauses that show that a person or thing has been affected or caused by an action.

1 You can often give more information about a noun, or an indefinite pronoun such as `someone’ or `something’, by adding a clause beginning with an `-ing’ form, an `-ed’ form, or a `to’-infinitive.
He gestured towards the box lying on the table.
I think the idea suggested by Tim is the best one.
She wanted someone to talk to.

2 You use an `-ing’ clause after a noun to say what someone or something is doing or was doing at a particular time.
The young girl sitting opposite him was his daughter.
Most of the people strolling in the park were teenagers.

3 You can also use an `-ing’ clause after a noun to say what a person or thing does generally, rather than at a particular time.
Problems facing parents should be discussed.
The men working there were not very friendly.

4 You often use an `-ing’ clause after a noun which is the object of a verb of perception, such as `see’, `hear’, or `feel’.
See also Unit 72.

Suddenly we saw Amy walking down the path.
He heard a distant voice shouting.
I could feel something touching my face and neck , something ice-cold.

5 You use an `-ed’ clause after a noun to show that someone or something has been affected or caused by an action.
He was the new minister appointed by the President.
The man injured in the accident was taken to hospital.

Remember that not all verbs have regular `-ed’ forms.
A story written by a young girl won the competition.
She was wearing a dress bought in Paris.