Wordwatch Towers

A plain language guide to punctuation, grammar and writing well.

Non-defining and defining clauses

with 4 comments

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Commas can be used to separate additional information in a sentence. For example:

The climbers, who were injured, were rescued.

You can see that this sentence would work just as well without the extra information about the climbers being injured:

The climbers were rescued.


Imagine a group of climbers on a mountain, but only some of them are injured. I want to explain that the injured climbers were rescued, but the others stayed where they were. In this case, my sentence would read:

The climbers who were injured were rescued.

This tells us that only the injured climbers were rescued.

Another example

Look at these two sentences:

The fathers, who had children with them, were allowed in first.

The fathers who had children with them were allowed in first.

In the first sentence we are given extra information about the fathers (they had children with them).

In the second sentence we are told that only those fathers with children were allowed in first.

Technical stuff

Non-defining clauses

Extra information provided between commas in a sentence is known as a ‘non-defining clause’. In the following sentence, the non-defining clause is in bold:

The climbers, who were injured, were rescued.

Defining clauses

In the following sentence, we are told that only the injured climbers were rescued. In other words,  the rescued climbers are defined as injured. The part of the sentence that tells us this is called a defining clause:

The climbers who were injured were rescued.


Extra information in a sentence is called a non-defining clause. Extra (or non-defining) information is always placed between commas.

Information that defines exactly who or what the sentence is about is called a defining clause. Defining information is not placed between commas.

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4 Responses

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  1. I thought a defining clause was one of those things in small print at the start of your 10-page loan contract. You know: “Borrower (hereinafter ‘YOU’) agrees that….”

    Michael Farrell

    08/04/2010 at 4:03 pm

    • Yes, in such cases, ‘defining clause’ means, ‘You won’t understand this bit so don’t bother reading it, then when you default on your loan you won’t have a leg to stand on’. Only a few grammar books give this secondary meaning.


      08/04/2010 at 4:35 pm

      • I like how, maybe ten years ago, some marketing folks told the lawyers that by using “YOU” and other such friendly language, it’d make the lopsided, first-born-child, impenetrable adhesion contract more palatable to consumers.

        Michael Farrell

        08/04/2010 at 6:12 pm

        • The party of the first part finds itself in agreement with you.


          08/04/2010 at 6:22 pm

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