What is a Defining Relative Clauses?
A defining relative clause (also called a restrictive relative clause) gives essential information about the noun it modifies. It tells us which person, thing, place, or time we are talking about. Without it, the sentence would be unclear or incomplete.
For example: "The woman who called you is my sister" — we need the clause to know which woman. Compare this with a non-defining clause: "My sister, who called you, is a doctor." The first has a defining clause (no commas); the second has a non-defining one (note the commas).
Key rule: defining relative clauses never use commas. If you see commas around a relative clause, it is non-defining.
How to Form a Defining Relative Clause
Place the relative clause immediately after the noun it refers to. Connect it with a relative pronoun — or leave it out when the pronoun is the object of the clause.
Noun + relative pronoun (who / which / that / whose / where / when) + rest of clauseRelative Pronouns
| Pronoun | Refers to | Function | Example |
|---|---|---|---|
| who | People | Subject or object | The teacher who taught me is retiring. |
| which | Things / animals | Subject or object | The car which broke down was new. |
| that | People or things | Subject or object | The book that I bought is great. |
| whose | People or things | Possessive | The student whose essay won is in my class. |
| where | Places | Adverbial | This is the café where we first met. |
| when | Times | Adverbial | I remember the day when she arrived. |
| why | Reasons | Adverbial | That's the reason why I left. |
When to Use Defining Relative Clauses
Identifying people — who or that
We use who (or that in informal speech) when the noun refers to a person. The pronoun can be the subject or the object of the relative clause. Both who and that are correct; who is more formal.
- The man who lives next door is a retired professor.
- The nurse who treated me was very kind.
- She's the colleague that I told you about.
Identifying things — which or that
We use which (or that) when the noun refers to a thing, object, animal, or abstract concept. In everyday spoken English, that is used more often; which is preferred in formal and written English.
- The report which landed on my desk was eighty pages long.
- I can't find the keys that I left here.
- The film which won the award was directed by a newcomer.
Showing possession — whose
We use whose to show that something belongs to the noun. It replaces his / her / its / their and works for both people and things. Think of it as the possessive form of who and which.
- The author whose novel I read just won a major prize.
- We helped a family whose house had burned down.
- They live in a building whose roof needs replacing.
Referring to places and times — where and when
We use where after nouns of place and when after nouns of time. These are adverbial pronouns — they tell us where or when the action in the relative clause takes place.
- This is the town where I grew up.
- The hotel where we stayed had an incredible view.
- Do you remember the summer when we drove across Europe?
- There are moments when silence says more than words.
Omitting the relative pronoun (contact clauses)
When the relative pronoun is the object of the relative clause, we can leave it out entirely. This is called a contact clause and is very common in informal speech and writing. When the pronoun is the subject, it cannot be omitted.
- The book (that) I read last night was gripping.
- The person (who/that) she recommended was perfect for the job.
- The dog that bit him had no collar. (subject — cannot omit)
Relative Pronouns at a Glance
Defining vs. Non-defining Relative Clauses
This is one of the most tested contrasts in B1–B2 grammar. The difference is not just punctuation — it changes the meaning of the sentence entirely.
Defining (no commas)
The students who passed the exam celebrated.
Only the students who passed celebrated. The clause identifies which students — not all students celebrated.
Non-defining (with commas)
The students, who had studied hard, celebrated.
All the students celebrated. The clause just adds extra information — it does not identify which ones.
Defining — that is possible
The jacket that I bought is too small.
That can replace which or who in defining clauses. This is the most common spoken form.
Non-defining — that is NOT possible
My jacket, which I bought in Paris, is too small.
That cannot be used in non-defining clauses. Only who or which are correct here.
Quick test: does the clause tell you which specific person or thing? → Defining (no commas). Does it just add extra information about a noun already identified? → Non-defining (use commas).
Common Mistakes
Using commas around a defining clause
✗ The film, that I watched last night, was brilliant.
✓ The film that I watched last night was brilliant.
Defining relative clauses never take commas. Commas signal a non-defining clause, which adds extra information rather than identifying the noun. Remove the commas — or switch to a non-defining clause structure if the information really is optional.
Repeating the subject with a pronoun (double subject)
✗ The man who he lives next door is my uncle.
✓ The man who lives next door is my uncle.
The relative pronoun (who / which / that) already acts as the subject of the relative clause. Do not add another pronoun (he / she / it / they) — this creates a double subject.
Using which for people
✗ The doctor which treated me was excellent.
✓ The doctor who treated me was excellent.
Which refers to things, not people. Use who (or that informally) for people. Using which for a person sounds unnatural and is marked as incorrect in formal writing and exams.
Omitting the relative pronoun when it is the subject
✗ The dog bit him had no collar.
✓ The dog that bit him had no collar.
You can only drop the relative pronoun when it is the object of the clause. When it is the subject (i.e. it performs the action of the verb), it must be included.
Using that in a non-defining clause
✗ My sister, that lives in London, is a nurse.
✓ My sister, who lives in London, is a nurse.
That is only used in defining (no-comma) relative clauses. Non-defining clauses require who for people and which for things. Check for commas as your trigger.
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