Differences Defining and Non-Defining Relative Clauses

The difference between defining and non-defining relative clauses is important to understand if you want to use relative clauses correctly. 

Relative clauses add extra information to a sentence by defining a noun. However…

• Defining relative clauses add essential information to a sentence and the clause cannot be omitted. 
• Non-defining relative clauses add non-essential information to a sentence and can be left out of a sentence without changing it’s meaning. 

Let’s take a closer look with some examples. 

What is the difference between a defining and non-defining relative clause?

Defining relative clauses are crucial to the sentence. If the clause is removed, the sentence will not make sense and will not have the same meaning. 

That is why they are also called essential relative clauses, essential meaning absolutely necessary or extremely important.

Let’s take a look with some examples! (The relative clause is in red).

Defining Relative Clauses:

• That is the woman

  who stole my handbag

  .

• This is the

  book

  that I read

  .

• The car

  that I d

  rive

  is a red Mercedes. 

Now lets see what happens if we take out the relative clause:

• That is the

  woman.

• This is the book.

• The car is a red Mercedes. 

As you can see the, the meaning of the sentences have been completely changed, or they don’t really mean anything. 

We now have questions about the noun:

• The woman who what?
• The book that what?
• What car?

Non-defining relative clauses, however, are not essential to the sentence. If the clause is removed, the sentence still makes sense and has the same meaning. 

The information may of course be relevant, which is why it is included, but it is not the main point that the sentence is trying to convey about the noun.

Non-Defining Relative Clauses:

• My grandmother,

  who is 86 years old

  , is coming on holiday with us this year.  

• My car, 

  which a Mercedes

  , can reach speeds of 140 km per hour. 

• Canberra, 

  which is the capital of Australia

  , is located at the northern end of the Australian Capital Territory

If we now take out the non-defining relative clauses, the main idea of the sentence remains and the sentence still makes perfect sense.

• My grandmother is coming on holiday with us this year.  
• My car can reach speeds of 140 km per hour. 
• Canberra is located at the northern end of the Australian Capital Territory.

What about commas in relative clauses?

You may have noticed another difference between defining and non-defining relative clauses, and that is with commas.

We’ll look at commas and relative clauses in more detail in another lesson, but basically defining relative clauses have no commas and non-defining do have commas:

Defining relative clause: 

• My plan is to buy the house

  that costs the least money

  .

Non-defining relative clause: 

• I’ll take the bus,

  which I think arrives in about ten minutes

  .

What about ‘that’ in relative clauses?

‘That’ is another important distinction in the difference between defining and non-defining relative clauses. 

You may have noticed that some relative clauses use ‘that’ while others do not. The basic difference is that:

• In defining relative clauses the words who or which can be replaced by that
• In non-defining relative clauses that cannot be used. 

In fact, it is much more common to use that instead of which in defining relative clauses, but it can also replace who.  

‘That’ in Defining Relative Clauses:

• It is my doctor

  who/that

  advised me to lose weight. 

• I’ll take the hat

  which/that

  fits me best.

• My boss is the person

  who/that

  usually leaves the office last.

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Non-defining relative clauses (also known as non-restrictive relative clauses) give us more information about a noun.
Non-defining relative clauses do not define or identify the noun.
Non-defining relative clauses are common in written English.

Example:
We visited Hyde Park, which is close to Buckingham Palace.

The underlined text “which is close to Buckingham Palace.” is the non-defining relative clause.
The non-defining relative clause gives us more information about Hyde Park.
It is not necessary to define or identify Hyde Park because there is only one Hyde Park in London.

We link the relative clause to the noun with a relative pronoun. In this example, the relative pronoun is “which“.

Punctuation rule

We use commas (,) to separate non-defining relative clauses from the rest of the sentence. Commas represent a pause.

Examples:

We visited Hyde Park, which is close to Buckingham Palace.
Hyde Park, which is close to Buckingham Palace, is closed today.

Relative pronouns used in non-defining relative clauses

In non-defining relative clauses we can use the following relative pronouns:

who
whom
which
whose

who

We use “who” for people only. It acts as the subject pronoun.

Example:
Mr Smith, who works with me, has invited me to a party. (subject pronoun)

In modern English, “who” is also commonly used as an object pronoun.
Example:
Mr Smith, who I like, has invited me to a party. (object pronoun)

Important: In very strict English, “who” is only used as a subject pronoun. In more formal English, only “whom” is used as an object pronoun.

whom

We use “whom” for people only. It acts as the object pronoun.

Example:
Mr Smith, whom I like, has invited me to a party. (object pronoun)

“whom” is only really used in very formal English. It is more common to use “who” as the object pronoun for people. In non-defining relative clauses, “who” and “whom” are NEVER replaced by “that”.

which

We use “which” for things or animals. It acts as the subject or object pronoun.

Examples:

He gave me a cake, which was on a white plate. (subject pronoun)
He gave me a cake, which I ate immediately. (object pronoun)

Normally we use “which” to give more information about a specific thing (noun).
Example: He gave me a cake, which was on a white plate.

But we can also use “which” to give more information about a whole clause.
Example 1:
He forgot to give me the cake, which was very annoying.
“which was very annoying” is not giving more information about the cake. It is giving us more information about the situation expressed in the whole clause “He forgot to give me the cake.”

Example 2:
Mark passed his driving test, which is fantastic.
“which is fantastic” is not giving more information about the driving test. It is giving us more information about the situation expressed in the whole clause “passed his driving test.”

Don’t forget the commas to separate the non-defining relative clause from the rest of the sentence.

In non-defining relative clauses, “which” is NEVER replaced by “that”.

Never use “that”

We never use the relative pronoun “that” in non-defining relative clauses.

Examples:

Mr Smith, who works with me, has invited me to a party.
Mr Smith, that works with me, has invited me to a party.

Mr Smith, whom I like, has invited me to a party.
Mr Smith, that I like, has invited me to a party.

He gave me the cake, which I ate immediately.
He gave me the cake, that I ate immediately.

We only use “that” in defining relative clauses.

whose

We use “whose” for people or things. “whose” acts as a possessive pronoun. This means it defines who owns something or who is related to someone.

Example:
Mark, whose brother works with me, wants to buy my house.

(Mark wants to buy my house.)
(Mark’s brother works with me.)

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