Defining and Non-defining Relative Clauses Practice Tests with B1 Grammar Rules & Examples

Defining and Non-defining Relative Clauses

When we want to give extra information about a person, place, or thing, we often use a relative clause. A relative clause is a part of a sentence that tells us more about a noun. It usually begins with a relative pronoun such as who, which, that, whose, or where.

There are two main types of relative clause in English:

• Defining relative clauses – these tell us which person or thing we are talking about. Without this information, the sentence does not make complete sense.
• Non-defining relative clauses – these add extra information about a person or thing. The sentence still makes complete sense without this information.

Look at these two examples:

The woman who lives next door is a doctor. (defining – we need this to know which woman)
My neighbour, who is a doctor, moved here last year. (non-defining – we already know who she is)

In this lesson, you will learn how to use both types of relative clause correctly, when to use commas, and which relative pronouns to use.

Defining Relative Clauses

A defining relative clause identifies exactly which person, place, or thing we mean. It answers the question: Which one?

Imagine there are many students in a classroom. You want to talk about one specific student:

The student who sits at the back is very quiet.

Without the relative clause "who sits at the back", we do not know which student you mean. The clause is essential to the meaning of the sentence.

Key Rules for Defining Relative Clauses

• There are NO commas before or after a defining relative clause.
• You can use that instead of who or which in defining relative clauses.
• In informal speech, you can sometimes leave out the relative pronoun when it is the object of the clause (see the section on omitting pronouns below).

Which Relative Pronoun to Use

Relative Pronoun	Used for	Example
who	people	The man who called was very polite.
which	things or animals	The book which I bought is really interesting.
that	people, things, or animals (informal)	The film that we watched was fantastic.
whose	possession (people, animals, things)	The girl whose bag was stolen was very upset.
where	places	The café where we met has closed down.

More Examples of Defining Relative Clauses

The woman who teaches us French is from Paris.
I need a phone that has a good camera.
He lives in a town where there is no train station.
The boy whose father is a pilot wants to fly planes too.
Can you pass me the bag which is on the table?

Non-defining Relative Clauses

A non-defining relative clause adds extra information about a person, place, or thing that we have already identified. This extra information is interesting, but we do not need it to understand the basic meaning of the sentence.

Imagine you are talking about your brother. There is only one brother, so your listener already knows who you mean:

My brother, who lives in Madrid, is visiting us next week.

If you remove the relative clause, the sentence still makes perfect sense: My brother is visiting us next week. The clause just adds a bonus fact.

Key Rules for Non-defining Relative Clauses

• Always use commas to separate a non-defining relative clause from the rest of the sentence. Think of the commas like brackets — they show that the information inside is extra.
• Never use "that" in a non-defining relative clause. You must use who, which, whose, or where.
• You cannot leave out the relative pronoun in a non-defining relative clause.

Which Relative Pronoun to Use

Relative Pronoun	Used for	Example
who	people	My teacher, who is very kind, gave us extra time.
which	things or animals	The Eiffel Tower, which was built in 1889, is in Paris.
whose	possession (people, animals, things)	My friend Sara, whose parents are teachers, loves reading.
where	places	We visited Rome, where we saw the Colosseum.

More Examples of Non-defining Relative Clauses

My cat, which is called Luna, sleeps all day.
The president, who gave a speech yesterday, will visit again next month.
Our flat, where we have lived for five years, is quite small.
Tom, whose sister I went to school with, has started a new job.
Barcelona, which is in the north-east of Spain, is famous for its architecture.

Defining vs Non-defining: Side-by-Side Comparison

The same words can appear in both types of relative clause, but the meaning — and the punctuation — changes completely. Look at these pairs:

Type	Sentence	Meaning
Defining	The students who studied hard passed the exam.	Only the students who studied hard passed — not all students.
Non-defining	The students, who studied hard, passed the exam.	All the students passed. (We are also mentioning that they studied hard.)
Defining	My sister who lives in London is a nurse.	I have more than one sister. This one lives in London.
Non-defining	My sister, who lives in London, is a nurse.	I have one sister. Extra fact: she lives in London.

Omitting the Relative Pronoun

In defining relative clauses only, you can sometimes leave out the relative pronoun. This is possible when the relative pronoun is the object of the clause (not the subject).

To understand this, think about who is doing the action:

The film that I watched was brilliant.

Here, I is doing the watching. That (= the film) is the object. So you can leave out that:

The film I watched was brilliant. ✅

But look at this sentence:

The man who called me was very friendly.

Here, who (= the man) is doing the calling. Who is the subject of the clause, so you cannot leave it out:

The man called me was very friendly. ❌

Quick Guide: Can You Leave Out the Pronoun?

Situation	Can you omit the pronoun?	Example
Defining clause — pronoun is the object	Yes ✅	The book (that) I read was great.
Defining clause — pronoun is the subject	No ❌	The woman who wrote this is famous.
Non-defining clause	No ❌	My dog, which loves walks, is very energetic.

Important Differences and Special Cases

"That" or "Which"?

Many learners are not sure whether to use that or which. Here is a simple rule to remember:

• Use that in defining relative clauses (for things and people, in informal English).
• Use which in non-defining relative clauses (for things).
• Never use "that" in a non-defining relative clause.

This is the bag that I bought in Italy. ✅ (defining)
This bag, which I bought in Italy, cost a lot of money. ✅ (non-defining)
This bag, that I bought in Italy, cost a lot of money. ❌ (never use "that" in non-defining)

"Whose" for Possession

Whose shows that something belongs to someone. It works for both defining and non-defining relative clauses.

The student whose essay was the best won a prize. (defining)
Maria, whose husband is a chef, loves cooking too. (non-defining)

Be careful: whose is not the same as who's (= who is).

The man whose car was stolen called the police. ✅ (possession)
The man who's talking is my uncle. ✅ (= who is)

"Where" for Places

Use where when the relative clause refers to a place.

The school where I studied was very old. (defining)
Edinburgh, where I grew up, is a beautiful city. (non-defining)

Common Mistakes

❌ My brother which is a doctor lives in Leeds.
✅ Use "who" for people, not "which". My brother, who is a doctor, lives in Leeds.

❌ The film, that we saw last night, was amazing.
✅ Never use "that" in a non-defining relative clause. The film, which we saw last night, was amazing.

❌ The woman who she works here is very helpful.
✅ Do not add an extra pronoun (she, he, it) after the relative pronoun. The woman who works here is very helpful.

❌ I live in a town where it is very quiet.
✅ Do not add "it" after "where". I live in a town where it is very quiet. → I live in a town that is very quiet. or I live in a very quiet town.

❌ The cat, whose it lives next door, is always in our garden.
✅ "Whose" already shows possession. Do not add "it". The cat, whose owner lives next door, is always in our garden.

❌ My mother who is a teacher is very patient. (when you only have one mother)
✅ Use commas for non-defining clauses about a unique person or thing. My mother, who is a teacher, is very patient.

❌ The book which I like it is on the shelf.
✅ Do not repeat the object after the relative pronoun. The book which I like is on the shelf.

Defining and Non-defining Relative Clauses: Quick Summary

Feature	Defining	Non-defining
Purpose	Identifies which person/thing	Adds extra information
Commas	No commas	Commas required
Can use "that"?	Yes ✅	No ❌
Can omit pronoun?	Yes (when object) ✅	No ❌
Remove clause — does sentence still make sense?	Not always	Yes, always
Relative pronouns used	who, which, that, whose, where	who, which, whose, where

Here are the key points to remember:

• A defining relative clause tells us which person or thing we mean. It has no commas and can use that.
• A non-defining relative clause gives us extra information. It always has commas and never uses "that".
• Use who for people, which for things, whose for possession, and where for places.
• Never add an extra pronoun (he, she, it, they) after the relative pronoun.
• In a defining relative clause, you can leave out the pronoun when it is the object of the clause.

Now practise defining and non-defining relative clauses in the exercises below.