Non-defining Relative Clauses
B1 IntermediateNon-defining relative clauses provide extra, non-essential information about a person, thing, or place. They are always separated from the rest of the sentence by commas.
Overview
A non-defining relative clause adds extra details to a sentence. If you remove this clause, the sentence still makes sense and the main subject remains clearly identified. These clauses are common in written English and formal speech to provide background information without starting a new sentence.
Form
Noun + , + relative pronoun + extra info + , + rest of sentence
The clause follows the noun it describes and must be enclosed in commas. You must use relative pronouns like who for people, which for things, or where for places. Unlike defining clauses, you cannot use the word that, and you cannot omit the relative pronoun.
Examples
Defining vs. Non-defining
In a defining clause, the information is essential to know who or what we are talking about. In a non-defining clause, the person or thing is already specific (often a proper name or a unique relation).
| Feature | Defining Clause | Non-defining Clause |
|---|---|---|
| Purpose | Identifies which person/thing | Adds extra information |
| Commas | No commas used | Always uses commas |
| Use of 'that' | Possible (e.g., The car that...) | Not possible |
Common mistakes
My car, that I bought last week, is blue.
My car, which I bought last week, is blue.
You cannot use 'that' in non-defining relative clauses.
My mother who is 60 loves gardening.
My mother, who is 60, loves gardening.
Commas are required to show the information is extra and not essential for identification.
Practice
Combine these sentences using a non-defining relative clause: 'London is the capital of the UK. It is on the River Thames.'
Show answer
London, which is on the River Thames, is the capital of the UK.
Answer:London, which is on the River Thames, is the capital of the UK.
Why:London is a specific proper noun, so the extra information about the river must be placed in a non-defining clause with commas and 'which'.
Correct the error: 'Mr. Smith, that is my teacher, is very kind.'
Show answer
Mr. Smith, who is my teacher, is very kind.
Answer:Mr. Smith, who is my teacher, is very kind.
Why:We use 'who' for people in non-defining clauses; 'that' is never used after a comma in this structure.
Is the following clause defining or non-defining? 'My sister, who lives in New York, is visiting today.'
Show answer
Non-defining
Answer:Non-defining
Why:The use of commas and the fact that 'My sister' is already a specific person indicates this is extra, non-defining information.