Everything you need to combine ideas into sophisticated sentences using relative clauses in English, defining vs non-defining, relative pronouns and exam practice.
📖 Reading time: ~13 minutes✅ Reviewed by a CELTA-qualified teacher🎯 Covers A1 to B2
A relative clause adds information about a noun without starting a new sentence, it's how English combines two separate ideas into one smoother, more sophisticated sentence. Instead of "I have a friend. She lives in Paris," we say "I have a friend who lives in Paris."
Relative clauses come in two distinct types, defining (essential information) and non-defining (extra, non-essential information), and knowing which type you're using changes both your punctuation and, in some cases, which relative pronoun is even allowed.
2. Quick Summary
⚡ Relative Clauses at a Glance
DefinitionA clause that gives more information about a noun, introduced by a relative pronoun.
Defining ClauseEssential information, no commas: "The man who called is my boss."
Non-Defining ClauseExtra information, needs commas: "My boss, who is very kind, called."
Common MistakeUsing "that" in a non-defining clause, or missing commas
Memory TipIf you can delete the clause and the sentence still makes clear sense, it's non-defining.
3. Relative Pronouns Recap
Pronoun
Used For
Example
who
People (subject)
the woman who called
whom
People (object, formal)
the man whom I met
which
Things, animals
the book which I read
that
People or things (defining clauses only)
the book that I read
whose
Possession
the man whose car was stolen
4. Defining Relative Clauses
A defining (or "restrictive") relative clause gives essential information, without it, we wouldn't know which person or thing is being talked about. No commas are used.
The woman who lives next door is a doctor. (essential, tells us which woman)
I read the book that you recommended. (essential, tells us which book)
5. Non-Defining Relative Clauses
A non-defining ("non-restrictive") relative clause adds extra, non-essential information. The sentence still makes complete sense without it. Commas are required around the clause.
My sister, who lives in Paris, is visiting next week. (extra detail, we already know who "my sister" is)
London, which I visited last year, is a fascinating city.
⚠️
"That" is never used in non-defining clauses
You can say "the book that I read" (defining) but never "London, that I visited, is...", non-defining clauses only ever use who/which/whose, never "that."
6. Defining vs Non-Defining, Side by Side
Defining
Non-Defining
Essential information
Extra, removable information
No commas
Commas required
Can use "that"
Cannot use "that"
Pronoun can sometimes be omitted
Pronoun can never be omitted
7. When You Can Omit the Relative Pronoun
In a defining relative clause, if the relative pronoun is the object of the clause (not the subject), it can often be dropped entirely, especially in speech.
With Pronoun
Pronoun Omitted
Can Omit?
The book that I read was great.
The book I read was great.
✅ Yes, object of the clause
The woman who called is my aunt.
,
❌ No, subject of the clause
8. Relative Adverbs, where, when, why
Adverb
Used For
Example
where
Place
the café where we met
when
Time
the day when we arrived
why
Reason
the reason why I called
9. Common Mistakes
❌ Incorrect
✅ Correct
Why
My sister who lives in Paris is visiting. (should be non-defining, extra info)
My sister, who lives in Paris, is visiting.
If there's only one sister, the clause is extra information and needs commas.
London, that I visited last year, was amazing.
London, which I visited last year, was amazing.
"That" is never used in non-defining clauses.
The man which called is my boss.
The man who called is my boss.
"Which" is used for things, not people, use "who" or "that."
The woman who I met her is my colleague.
The woman who I met is my colleague.
Don't repeat the object with an extra pronoun, the relative pronoun already covers it.
10. Exercises
A. Gap Fill, Complete with the correct relative pronoun/adverb (10 questions)
1. The woman ___ called is my aunt. (person, subject)
2. The book ___ I read was excellent. (thing, object)
3. My brother, ___ lives in Canada, is visiting. (non-defining, person)
4. This is the café ___ we first met. (place)
5. That's the man ___ car was stolen. (possession)
6. I don't remember the day ___ we arrived. (time)
7. The film ___ we watched last night was boring. (defining, thing)
8. Paris, ___ I visited last year, is beautiful. (non-defining, place)
9. That's the reason ___ I called you. (reason)
10. The man ___ helped me was very kind. (person, subject)
Show Answers (A)
1. who 2. that/which 3. who 4. where 5. whose 6. when 7. that/which 8. which 9. why 10. who
B. Multiple Choice (5 questions)
1. The woman ___ called is my aunt. (a) who (b) which
2. My sister, ___ lives in Spain, is visiting. (a) who (b) that
3. The book ___ I read was great. (a) that (b) who
4. London, ___ I visited last year, is beautiful. (a) which (b) that
5. The man ___ car was stolen is my neighbour. (a) whose (b) who
Show Answers (B)
1.a 2.a 3.a 4.a 5.a
C. Error Correction (5 questions)
1. London, that I visited last year, was amazing.
2. The man which called is my boss.
3. My sister who lives in Paris is visiting. (only one sister, should be non-defining)
4. The woman who I met her is my colleague.
5. The café which we met is closed now. (should be 'where')
Show Answers (C)
1. London, which I visited last year, was amazing. 2. The man who called is my boss. 3. My sister, who lives in Paris, is visiting. 4. The woman who I met is my colleague. 5. The café where we met is closed now.
D. Freer Practice, Write Your Own Sentences (2 tasks)
1. Write a defining relative clause about a person you know.
2. Write a non-defining relative clause about a place you've visited.
Show Answers (D)
Model answers will vary. Examples: 1. "The colleague who sits next to me is very funny." 2. "Barcelona, which I visited two years ago, has amazing architecture."
11. Mini Quiz
12. Exam Focus, Cambridge, IELTS, SELT
Exam
How Relative Clauses Are Tested
Sample Question
Cambridge B1 Preliminary / B2 First
Relative pronoun choice and comma placement in Use of English and Writing.
"The man ___ called is my boss." (who)
Cambridge C1 Advanced
Defining vs non-defining precision in complex sentence transformations.
Distinguishing when commas change meaning entirely.
IELTS Writing
Relative clauses add sentence variety and complexity, both scored under grammatical range.
Combining two ideas into one sophisticated sentence in Task 2 essays.
Trinity GESE/ISE (SELT)
Natural use when describing people and places in conversation.
"Tell me about someone who has influenced you."
13. Frequently Asked Questions
A clause that gives more information about a noun, introduced by a relative pronoun like who, which, that or whose.
Defining clauses give essential information with no commas; non-defining clauses give extra, removable information and always need commas.
No, 'that' is only used in defining relative clauses, never non-defining ones.
In a defining clause, when the pronoun is the object of the clause: 'The book (that) I read was great.'
Where, when and why, used to introduce clauses about place, time and reason, e.g. 'the café where we met.'
Try removing it, if the sentence still makes clear, complete sense, it's non-defining and needs commas.
Yes, they're a natural way to add detail when describing people and places, which comes up frequently in Trinity GESE/ISE speaking tests.
📅 Ready to Master Relative Clauses, and Every Other Grammar Point?
Reading about grammar takes you part of the way. Real fluency comes from using it, in conversation, with a tutor who corrects you immediately. Book a free level test with Elite Language Solutions and find out exactly where you are.