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Relative clauses


Grammatical form

noun (+ relative pronoun) + relative clause

I've got a book that had a complete list of irregular verbs.
This is the book we use in our English class.

noun, + relative pronoun + relative clause , + main clause

My English textbook, which I bought last summer, was quite expensive.

main clause, + relative pronoun + relative clause

He was reading a book, which was very unusual.


General usage

Relative clauses contain information about nouns. There are two main types: defining and non-defining. The form and usage of each is quite different.

Have you seen the book that I was reading this morning?

This is a defining relative clause and contains information about the noun book

The River Nile, which is over 6,500 kilometres long, is Egypt's main source of water.

This is a non-defining relative clause and contains information about the noun the River Nile.
The information in the first example, that I was reading this morning, identifies the book - it tells us which book. The information in the second example, which is over 6,500 kilometres long is extra information.
The main differences between the two types of clauses are summarized below.

Defining and non-defining relative clauses

Defining relative clausesNon-defining relative clauses
  • identify a noun - i.e. say which person, place, thing etc. is meant
  • are not separated by commas
  • use the pronouns which or that for things and who or that for people
  • can be formed without a relative pronoun when the pronoun is not the subject of the relative clause
  • cannot be removed from a sentence, otherwise the sentence will be ungrammatical or unclear
  • are common in both spoken and written English
  • give extra information about a person, place, thing etc.
  • are separated by commas
  • do not use that as a relative pronoun

  • are always formed with a relative pronoun

  • can be removed from a sentence and the sentence will still be grammatical

  • are more common in written English and formal spoken English (speeches, TV news reports etc.)

For more, see detailed notes on each type of relative clause:
defining relative clauses
non-defining relative clauses




ESL quizzes for Relative clauses
Relative clauses and pronouns
Ten-question multiple-choice quiz testing both defining and non-defining clauses


Comparison with as...as...

Comparison with <i>as</i>...</i>as...</as>: picture
Detailed grammar reference notes on comparison with as....
Three pages, illustrated. Includes positive and negative forms, modifiers and common similes.
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Download Comparison with as...as - grammar notes (PDF)