Short answer: A relative clause adds information about a noun using who, which, that, whose, where or when. If the clause tells you which thing you mean, it is defining and takes no commas.
If it adds extra information about something already clear, it is non-defining, goes between commas, and cannot use that. Get that one rule right and relative clauses become one of the safest ways to show range.
Relative clauses count toward the "variety of complex structures" the Band 7 descriptor asks for, and they are easy to use accurately once the comma rule is clear. All examples below were written for this article.
Which relative pronoun?
| Pronoun | Refers to | Example (written for this article) |
|---|---|---|
| who | People | Students who work part-time often manage their time better. |
| which | Things, ideas | The policy, which was introduced in 2020, reduced traffic. |
| that | People or things, defining only | The country that recycled the most was Germany. |
| whose | Possession | Families whose children attend private schools pay twice. |
| where | Places | Cities where rents are high lose young workers. |
| when | Times | The 1990s were a decade when car ownership doubled. |
Defining vs non-defining: the comma rule
Defining clauses are essential to the meaning. Remove them and you no longer know which thing is meant:
People who exercise regularly live longer. (Not all people, only those who exercise.)
Non-defining clauses add extra information about something already identified. Remove them and the sentence still makes sense:
My brother, who lives in Dhaka, is a doctor. (I have one brother; the clause just adds detail.)
Two rules follow. Non-defining clauses always go between commas, and they never use that: The report, that was published in May, is wrong; write The report, which was published in May,.
Sentence-level "which": linking data to meaning
A which clause can refer back to a whole idea, not just one noun. This is especially useful in Task 1, where you report a figure and then its significance, and in Task 2, where you state a fact and then its consequence:
- Coal use fell by half between 2000 and 2020, which suggests that renewable sources replaced it.
- Many graduates cannot find work in their field, which leads some to question the value of a degree.
Always put a comma before a sentence-level which.
Reduced relative clauses
You can often drop the pronoun and be to make a sentence tighter. This is common in Task 1:
- the data (which is) shown in the chart → the data shown in the chart
- people (who are) living in rural areas → people living in rural areas
- the figures (that were) recorded in 2010 → the figures recorded in 2010
In a defining clause where the relative pronoun is the object, you can drop it entirely: the essay (that) I wrote. Both versions are correct.
Common relative clause errors
| Error | Wrong | Right |
|---|---|---|
| that after a comma | The museum, that opened in 2015, is free. | The museum, which opened in 2015, is free. |
| which for people | Teachers which are experienced earn more. | Teachers who are experienced earn more. |
| Repeated subject | The man who he called me was my uncle. | The man who called me was my uncle. |
| whose vs who's | A country who's economy is growing. | A country whose economy is growing. |
| Missing comma on a non-defining clause | London which is the capital is expensive. | London, which is the capital, is expensive. |
Relative clauses in Speaking
In Part 2, relative clauses are the natural way to describe a person or place: It's a small café near my office, where I usually go on Fridays. In speech, that and who are often interchangeable for people in defining clauses, and dropping the object pronoun (the book I read) sounds more natural than keeping it.
Practice: join the sentences
- The survey asked 2,000 adults. The survey was published last year.
- I have a friend. Her father is a pilot.
- Rent rose by 30%. This forced many families to move.
Answers: (1) The survey, which was published last year, asked 2,000 adults. (2) I have a friend whose father is a pilot. (3) Rent rose by 30%, which forced many families to move.
Next: complex sentences, punctuation for IELTS and conditionals.