How to use defining and non-defining relative clauses

Have you ever studied ‘relative clauses’ and thought they were confusing? You’re not the only one! In this blog I will explain the difference between defining and non-defining relative clauses.

What is a relative clause?

A relative clause is part of a sentence which adds more information about a thing in the postmodifer position. For example:

(1) The guitar which is black belongs to John.

The relative clause “which is black” adds more information about the thing (guitar).

Here’s another relative clause:

(2) The guitar, which is black, belongs to John.

“Wait a minute,” you say. “Sentence (2) is just the same as sentence (1), only sentence (2) has an extra comma.”

Although the sentences look the same, they do not have the same meaning. Sentence (1) is defining and sentence (2) is non-defining. Let me explain.

 

Defining relative clauses

Example: The guitar which is black belongs to John.

If I show you 3 guitars and say “The guitar which is black belongs to John”, do you know which guitar belongs to John?

Of course not, because they’re all black! The information “which is black” should help you to identify John’s guitar. But in this case, since all the guitars are black, the defining information does not help at all.

But what about now:

The guitar which is black belongs to John.

Now you know that John’s guitar is “C” because the information “which is black” identifies or defines John’s guitar. Since each guitar is a different colour, we can identify or define John’s guitar by its colour.

 

Non-defining relative clauses

Example: The guitar, which is black, belongs to John.

In this case, the information “which is black” does not identify or define John’s guitar. It just tells us what colour the guitar is.

We don’t need to define John’s guitar by its colour, because clearly “C” is the only guitar.

One more thing

If we read aloud the sentence with the defining relative clause:

The guitar which is black belongs to John.

We don’t pause between “guitar” and “which”. This proves that the clause “which is black” is part of the noun group. In fact, defining relative clauses are rank-shifted.

However, if we read aloud the sentence with the non-defining relative clause:

The guitar, which is black, belongs to John.

We must pause between “guitar” and “which”. This proves that the clause “which is black” is not part of the noun group. It is separate because it does not define the guitar. This is why there is a comma between “guitar” and “which”.

 

So in summary, defining relative clauses give information which identifies the thing, and this information is part of the noun group.

 

 

 

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