1. Relative clauses describe the preceding noun.

2. There are two types of relative clauses:
a) A philatelist is a person who collects stamps.
b) I had a very interesting meeting with Dr Evans, who collects stamps and butterflies in his spare time.

3. Defining relative clause Non-defining relative clause
A philatelist is a person who collects stamps.
Non-defining relative clause
I had a very interesting meeting with Dr Evans, who collects stamps and butterflies in his spare time.
It gives us essential information.
It adds extra information of secondary importance.
It cannot be left out.
It can be left out of the sentence.

4. Defining relative clause Non-defining relative clause
A philatelist is a person who collects stamps.
Non-defining relative clause
I had a very interesting meeting with Dr Evans, who collects stamps and butterflies in his spare time.
There are no commas before and after defining relative clauses when written.
There are commas before and after non-defining relative clauses when written.
There are no pauses when spoken.
There are pauses when spoken.

5. Relative pronouns Defining Non-defining Person Thing Subject who
(that)
that
(which)
which
Object
whom
Possessive
whose

6. Defining relative clauses
The forms in brackets are possible but not as common.

7. Defining relative clauses - examples
Subject (persons)
The woman who is wearing blue shorts is my wife.
The boy who lives next door has gone to hospital.

8. Defining relative clauses - examples
Subject (things)
Is this the letter that came yesterday?
What was the name of the horse that won the race?

9. Defining relative clauses
The relative pronoun can be left out if it refers to the object of the relative clause.

10. Defining relative clauses - examples
Object (persons)
The person (that) you need to talk to is on holiday.
The man (that) you met yesterday was my father.

11. Defining relative clauses - examples
Object (things)
This is the best wine (that) I’ve ever tasted.
The road (that) we wanted to take was blocked.

12. Defining relative clauses - examples
Possessive
That’s the woman whose son won the first prize.
Which is the dog whose owner recently died leaving it her fortune?

13. Non-defining relative clauses
Relative pronouns in non-defining relative clauses cannot be left out.

14. Non-defining relative clauses
That is not used in non-defining relative clauses!

15. Non-defining relative clauses - examples
Subject (persons)
Mr Jenkins, who has written several books, spoke at the meeting last night.
My neighbour, who is very pessimistic, says there will be no apples this year.

16. Non-defining relative clauses - examples
Subject (things)
The 8.15 train, which is usually punctual, was late today.
Smallpox, which once killed thousands of people every year, has now been wiped out.

17. Non-defining relative clauses - examples
Object (persons)
Peter, whom everyone suspected, turned out to be innocent.
She introduced me to her husband, whom I hadn’t met before.

18. Non-defining relative clauses - examples
Mr Travis, who I was working for, was very generous.
(informal) or
Mr Travis, for whom I was working, was very generous.
(formal)

19. Non-defining relative clauses - examples
Object (things)
She gave me this jumper, which she had knitted herself.
These books, which you can get at any bookshop, will give you all the information you need.

20. Non-defining relative clauses - examples
His house, for which he paid £10,000, is now worth £50,000. or
His house, which he paid £10,000 for, is now worth £50,000.

21. Non-defining relative clauses - examples
Possessive
My parents, whose greatest ambition is to retire to the coast, have just sold their house.
His house, whose windows were all broken, was a depressing sight.

22. The importance of commas
My American cousin who you met last summer is coming to stay again.
My American cousin, who you met
last summer, is coming to stay again.

23. The importance of commas
The flowers which my boyfriend sent look beautiful in my new vase.
The flowers, which my boyfriend sent, look beautiful in my new vase.

24. Sentence-relative
Sometimes a relative clause refers not just to the noun before it but to the whole sentence before.

25. Compare: He showed me a photo that upset me.
He showed me a photo, which upset me.

26. The clock struck thirteen, which made everyone laugh.
In these clauses we always use a comma and the relative pronoun which.
The clock struck thirteen, which made everyone laugh.

27. Relative adverbs why, what – can be used in DR clauses only
when, where – can be used in both DR and NDR clauses
I don’t know why we’re arguing.
Has she told you what is worrying her?

28. Tell me when you expect to arrive.
We go walking on Mondays, when the rest of the world is working.
The hotel where we stayed was excellent.
He works in Oxford, where my sister lives.

29. Bibliography
English Grammar in Use Supplementary Exercises by Louise Hashemy with Raymond Murphy
Language Practice by Michael Vince with Paul Emmerson
Grammar Practice by Elaine Walker, Steve Elsworth
A Practical English Grammar by A.J. Thompson and A.V. Martinet