Relative clauses are introduced by relative pronouns like who, which, that, whose or relative adverbs like where and when. There are two types of relative clauses: defining clauses that provide essential information about a noun and are not separated by commas, and non-defining clauses that provide extra information and are separated by commas. Defining clauses cannot omit the relative pronoun/adverb or use "that", while non-defining clauses cannot omit the relative word.

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Relative Clauses

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Relative clauses are introduced by relative
pronouns ( who, which, that, whose ) and
relative adverbs (where, when ).
PRONOUNS
PEOPLE Who / that
THINGS/ANIMAL
S/IDEAS
Which / that
POSSESSION Whose
ADVERBS
PLACE Where
TIME When

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We have two types of relative
clauses:
Defining
S + V + Relative adverb/pronoun + V
We can meet at the café which is on Grandview.
S + Relative adverb/pronoun + S + V + V
The place where I live is beautiful.
Non-defining
S + ,Relative adverb/pronoun + V, + V
Facebook , which is a social network, is popular.

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Defining relative clauses
 Give information which is needed to understand the
meaning of the sentence. They are NOT separated
from the man clause by commas.
She’s the girl who/that lives next door.
The book (which/that) you bought is on the desk.

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NOTE
• Who, Which and That can be omitted if they
refer to the object of the sentence. Whose and
Where cannot be omitted.
• In formal language prepositions appear at the
beginning of relative clause.
The chair on which I am sitting isn’t very
confortable.
• In informal language they appear at the end
of the relative clause.
The chair (which /that) I’m sitting on isn`t very
confortable.

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Non-defining relative clauses
Give extra information about the person, thing or
idea they refer to. They are always separated from
the main clause by commas.
Mr Brown, who is our Geography teacher, is quite old.
Our car, which cost us a lot, keeps breaking down.

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NOTE
• Relative pronouns / adverbs cannot be
omitted in non-defining relative clauses; nor
can we us That instead of them.
• Prepositions usually appear at the beginning
of non-defining relative clauses.
This cupboard, in which I keep my old toys,
hasn`t been cleaned for ages.
• Which may also refer to a whole sentence.
He offered to give me a lift, which was very kind
of him.