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grammar  >  relative clauses - non-defining




subject , + relative pronoun + relative clause , + main clause

(1) The River Nile, which is over 6,500 kilometres long, is Egypt's main source of water.
(2) The modern Olympic Games, which take place every four years, were first held in 1896.


General use of non-defining relative clauses

 


Non-defining relative clauses contain information about a noun.
Example (1) contains information about the River Nile.
Example (2) contains information about the modern Olympic Games.

The are called non-defining or non-identifying relative clauses to avoid confusion with defining relative clauses.

Non-defining relative clauses contain extra information about the noun to which they relate.
They do not tell us which person or thing that we are talking about.
It is already clear which person or thing we are talking about without the relative clause.

Example (1)
The river Nile - It is quite clear what we are talking about - there is only one river Nile.
The relative clause which is over 6,500 kilometres long is extra information.

Example (2)
The modern Olympic Games - It is quite clear what we are talking about - there is only one modern competition called the Olympic Games.
The relative clause which take place every four years is extra information.

Sentences containing non-defining relative clauses remain grammatical and have meaning if you remove the non-defining relative clause :

Example (1) - relative cluase removed
The River Nile is Egypt's main source of water.
This is a complete grammatical sentence.

Example (2) - relative cluase removed
The modern Olympic Games were first held in 1896.
This is a complete grammatical sentence.

By contrast, defining relative clauses often do not make sense when the defining reltative clause is removed or it is unclear exactly what you are talking about.

Examples:
(3)
Have you read the message that I sent you yesterday?

The defining relative clause, that I sent you yesterday contains very important information. It tells us which message. Without this clause we only have:

Have you seen the message?
This sentence grammatically complete, but it is unclear which message the speaker means.

(4)
That's the hotel we stayed in last year.
The defining relative clause we stayed in last year contains essential information about the hotel. Without it we only have:

That's the hotel
This makes little sense on its own.

For more, see: defining relative clauses.

Position of the relative pronoun

 


The relative pronoun usually comes immediately after the noun that it relates to.

Consider this example :
The Eiffel Tower, which was built in 1887, is not far from the Louvre museum.

The relative clause, which was built in 1887, relates to the Eiffel Tower.

If you want to add a non-defining relative clause to the Louvre museum, it must go immediately after the word museum:

The Eiffel Tower is not far from the Louvre museum, which contains the famous portrait, the Mona Lisa.

Punctuation : commas

 


Non-defining relative clauses are separated from the rest of the sentence by commas.
Non-defining relative clauses which relate to the whole of the main clause

 


Relative clauses usually relate to one noun or noun phrase. However some non-defining relative clauses can relate to the whole of the main clause of the sentence.

Consider these examples :

(1) We had some ice-cream for dessert, which was very unusual.
(2) We had some ice-cream for dessert which was very unusual.


In (1), the non-defining relative clause which was very unusual, relates to the whole of the main clause. i.e. It was unusual for them to have ice-cream for desert - they do not usually eat ice-cream for dessert.

In (2), the defining relative clause which was very unusual, relates only to the ice-cream - it was an unusual type of ice-cream, e.g. it was chicken flavoured, or black in colour etc.
Choice of relative pronoun

 


Use which for objects (things).
Do not use that in non-defining relative clauses
The station, which was built in 1906, is due to be demolished.

Use who for people.
Do not use that in non-defining relative clauses
John Woo, who was born in China, has made a successful career in Hollywood.

Use whose for possessives.
The author, whose works have been translated into over 50 languages, is working on a new novel.

Use where or preposition + which (formal) for places.
The family home in New Orleans, where Munroe spent much of his childhood, has recently been opened to the public.

The family home in New Orleans, in which Munroe spent much of his childhood, has recently been opened to the public.

Use when or preposition + which for times.
Christmas Day, when many people stay at home, is a quiet day in many western countries.

Christmas Day, on which many people stay at home, is a quiet day in many western countries.
Omitting the relative pronoun

 


The relative pronoun is never omitted with non-defining relative clauses.