Relative Clauses in English: Defining and Non-defining Explained

Relative clauses are an important part of English grammar because they help us join ideas and add information about people, things, places, and time. In this lesson, you will learn how relative clauses work, what the difference is between defining and non-defining relative clauses, and how to use them correctly in your writing and speaking.

What is a relative clause?

A relative clause gives us more information about a noun. We usually use it to join two ideas into one sentence.

Compare these two sentences:

• I met our new neighbour. She lives on the first floor.
• I met our new neighbour who lives on the first floor.

Here, who lives on the first floor is the relative clause.

Another example:

• My sister is moving to Scotland. She is younger than me.
• My sister, who is younger than me, is moving to Scotland.

In both cases, the relative clause adds information about a noun. However, the two clauses are not the same type.

The two types of relative clauses

There are two main types of relative clauses:

• Defining relative clauses
• Non-defining relative clauses

The difference between them is simple:

• A defining relative clause gives essential information. It tells us exactly which person or thing we mean.
• A non-defining relative clause gives extra information. The sentence would still make sense without it.

Let’s look at the difference:

• I met our new neighbour who lives on the first floor.
  → This tells us which neighbour we mean.
• My sister, who is younger than me, is moving to Scotland.
  → This gives us extra information about my sister. We already know who she is.

Relative pronouns

We usually introduce relative clauses with these relative pronouns:

• who
• which
• that
• whose
• where
• when

We use them to connect the relative clause to the noun it describes.

For example:

• That is the woman who helped me.
• This is the book which I told you about.
• He is the man whose daughter is a doctor.
• That is the house where I grew up.
• Summer is the time when we usually travel.

Relative clauses come after the noun

Relative clauses usually come immediately after the noun they describe.

• Thomas turned on the computer which he had bought the previous day.
• Here are the people who want to buy our car.
• My husband, who is a teacher, teaches French.

Defining relative clauses

We use defining relative clauses to give information that is necessary to identify the person or thing we are talking about.

Without the defining clause, the meaning would be incomplete or unclear.

Examples

• The man who is our host is Irish.
• Why don’t you ask the boy who is sitting next to you?
• The boy who bullied the other children was punished.
• We bought a TV which was quite inexpensive.
• This is the man whose dog is a champion.
• There is a man at the door who wants to see you.

In all of these sentences, the relative clause helps us identify the noun.

For example:

• The man is Irish
  → Which man?
• The man who is our host is Irish
  → Now the meaning is clear.

Can we omit the relative pronoun?

In defining relative clauses, we can sometimes leave out who, which, or that — but only when it refers to the object of the clause, not the subject.

We can omit it:

• I need the clothes (which/that) I feel comfortable in.
• I found the book (which/that) you were looking for.
• That’s the man (who/that) I told you about.

We cannot omit it:

• The woman who lives next door is a dentist.
• The car that broke down was brand new.

Why not? Because in these sentences, who and that are the subjects of the relative clause.

A useful thing to remember

If you remove a defining relative clause, the sentence often loses its essential meaning.

• Sara’s parents have finally met the man who went to college with her.

Without the clause, we get:

• Sara’s parents have finally met the man.

That sentence is grammatically correct, but the important identifying information is gone.

Non-defining relative clauses

We use non-defining relative clauses to add extra information about a person or thing that is already clear.

These clauses do not tell us which person or thing we mean. They simply add more detail.

Examples

• Rob and Simona, who are cousins, go to the same class.
• My mother, who comes from Wales, loves cooking.
• Tom, who was very hungry, couldn’t wait any longer for his break.
• My boss, who noticed that I looked tired, gave me a day off.
• Romeo and Juliet, whose families hated each other, were lovers.

In these examples, the relative clause gives additional information, but it is not essential.

For example:

• My mother loves cooking.
  This sentence already makes perfect sense.

The clause who comes from Wales simply adds extra detail.

Important rules for non-defining relative clauses

1. Use commas

Non-defining relative clauses are separated from the rest of the sentence by commas.

• My brother, who lives in Bristol, is visiting us next week.
• Paris, which is one of my favourite cities, is beautiful in spring.

2. Do not use that

In non-defining relative clauses, we do not use that.

• My car, which I bought last year, is already giving me problems.
• My car, that I bought last year, is already giving me problems. ✗

3. Do not omit the relative pronoun

Unlike defining clauses, the relative pronoun in a non-defining clause cannot be left out.

• My teacher, who helped me a lot, retired last year. ✓
• My teacher, helped me a lot, retired last year. ✗

Defining vs non-defining: the key difference

Look at these two sentences:

• The students who work hard usually do well.
• My students, who work hard, usually do well.

The first sentence means that only the students who work hard do well.

The second sentence means that all my students work hard, and this extra information is simply being added.

That little pair of commas changes the meaning quite a lot. Grammar has a wicked sense of humour sometimes.

Common mistakes learners make

1. Using commas with defining clauses

• The book, that I borrowed from you, is excellent. ✗
• The book that I borrowed from you is excellent. ✓

2. Using that in non-defining clauses

• My aunt, that lives in Leeds, is coming tomorrow. ✗
• My aunt, who lives in Leeds, is coming tomorrow. ✓

3. Omitting the pronoun in non-defining clauses

• My car, I bought last year, is very reliable. ✗
• My car, which I bought last year, is very reliable. ✓

4. Forgetting that the clause must describe the noun before it

• I spoke to the teacher of the boy who was angry.
  This could mean the boy was angry, or the teacher was angry. Be careful with sentence structure when the meaning could be unclear.

Exercise: Join the sentences using a relative clause

Join each pair of sentences to make one sentence with a relative clause.

1. They gave away the cat. It was afraid of mice.
2. That’s the man. I was telling you about him.
3. Paul caught the 10 o’clock train. It doesn’t get in till 11.30.
4. The doctor thought Rita looked tired. He gave her the day off.
5. Simon had only half an hour for lunch. He couldn’t wait any longer.
6. Sean is looking after some children. They are very spoiled.
7. An old man brought in a small girl. Her hand was bleeding.
8. Dean was waiting for a girl. She didn’t turn up.
9. The company is sending me to London. I work for this company.
10. The boy was an actor. I was sharing an apartment with this boy.
11. The restaurant was noisy. We were having lunch in that restaurant.

Answer key

1. They gave away the cat, which was afraid of mice.
2. That’s the man who/that I was telling you about.
3. Paul caught the 10 o’clock train, which doesn’t get in till 11.30.
4. The doctor, who thought Rita looked tired, gave her the day off.
5. Simon, who had only half an hour for lunch, couldn’t wait any longer.
6. Sean is looking after some children who are very spoiled.
7. An old man brought in a small girl whose hand was bleeding.
8. Dean was waiting for a girl who didn’t turn up.
9. The company which/that I work for is sending me to London.
10. The boy who/that I was sharing an apartment with was an actor.
11. The restaurant where we were having lunch was noisy.

Relative Clauses: Defining and Non-defining Printable practice worksheet with mixed exercises and answer key  in downloadable PDF

Final thoughts

Relative clauses help you combine ideas smoothly and make your English sound more natural, more connected, and more advanced. The main thing to remember is this:

• Defining relative clauses identify the noun and are essential.
• Non-defining relative clauses add extra information and are separated by commas.

Once you get used to that difference, the rest becomes much easier.

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FAQ 

What is a relative clause in English?

A relative clause is a part of a sentence that gives more information about a noun. It usually begins with a relative pronoun such as who, which, that, whose, where, or when.

What is the difference between defining and non-defining relative clauses?

Defining relative clauses give essential information about a noun, while non-defining relative clauses give extra information that is not necessary for the basic meaning of the sentence.

Can you omit the relative pronoun in English?

Yes, you can sometimes omit who, which, or that in defining relative clauses when the pronoun refers to the object. You cannot omit it when it refers to the subject, and you cannot omit it in non-defining relative clauses.

Do non-defining relative clauses need commas?

Yes, non-defining relative clauses must be separated from the rest of the sentence with commas.

Can we use that in non-defining relative clauses?

No, we do not normally use that in non-defining relative clauses. We usually use who, which, whose, where, or when instead.