🎓 Prepared by students from Boğaziçi University

What are Non-Defining Relative Clauses?

Non-defining relative clauses (also called non-restrictive or appositive clauses) provide extra information about a noun that is already identified. Unlike defining clauses, they add additional detail rather than restrict which person or thing is being talked about.

Short answer

A non-defining relative clause is a subordinate clause that adds extra information about an already-identified noun and can be removed without changing the main meaning. It uses relative pronouns like who, which, or whom, and is separated by commas.

How Non-Defining Clauses Work

1
Identify the noun
The noun is already clear (e.g., 'My brother')
↓
2
Add extra detail
Insert a clause with commas (e.g., 'who is a doctor')
↓
3
Test removal
Clause can be omitted: 'My brother is happy'
↓
4
Sentence still makes sense
The core meaning remains unchanged

Step-by-step worked examples

Add a non-defining clause to: My father is an engineer.

The noun 'father' is already identified (mine specifically).
Add extra info in commas: My father, who has worked in oil & gas, is an engineer.
Or: My father, who studied at MIT, is an engineer.

Identify the non-defining clause: The new movie, which was filmed in Iceland, is out next week.

The noun is identified: 'the new movie'
Non-defining clause (in commas): 'which was filmed in Iceland'
Test: 'The new movie is out next week' — still clear!

Why are commas needed here? John, who is my best friend, got a promotion.

The noun is clear: 'John' (already identified as a specific person)
The clause 'who is my best friend' is extra detail, not identification.
Commas signal this is bonus info, not a restrictor.

Flashcards

Quick quiz

Q1.Which is a non-defining relative clause?

Correct answer: B. Option 2: 'My sister' is already identified; the clause adds extra info with commas.

Q2.Can you remove a non-defining clause?

Correct answer: B. Non-defining clauses are bonus information, not essential.

Q3.Use a non-defining clause: London is the capital of the UK.

Correct answer: C. Option 3 adds extra info about location with commas and 'which'.

Q4.Non-defining clauses never use…

Correct answer: D. 'that' only works in defining clauses. Non-defining uses who/which/where/when.

📄Download this topic as a printable worksheet (PDF)Summary + 10 questions + answer key — print it, share it in class.↓

Study better with Bounlu apps

Notek

The full card deck, worked steps and AI-tutor support for “What are Non-Defining Relative Clauses?” are in Notek — study by hand before your exam.

Get it free

PromyNever miss an exam or homework deadline with Promy: AI turns the dates in your inbox into reminders automatically.

Common mistakes

✗

Forgetting the commas around non-defining clauses. — Correct: Non-defining clauses MUST be separated by commas.

✗

Using 'that' in a non-defining clause. — Correct: Use 'who', 'which', 'whom', 'where', or 'when' — never 'that'.

✗

Thinking removal changes the meaning. — Correct: Removing non-defining info keeps the main idea intact.

✗

Using non-defining to identify an unknown noun. — Correct: Use defining (no commas) to identify; non-defining adds bonus details.

FAQ

What is a non-defining relative clause?

A clause that adds extra information (in commas) about an already-identified noun; removable without changing the main meaning.

How do defining and non-defining clauses differ?

Defining: identifies the noun (no commas, can't remove). Non-defining: adds extra info (commas, removable).

Why do non-defining clauses need commas?

Commas signal that the clause is extra detail, not essential to identifying the noun.

Can you use 'that' in non-defining clauses?

No, 'that' is only for defining clauses. Use 'who', 'which', 'whom', 'where', or 'when' instead.