Relative clauses are subordinate clauses that modify nouns, using relative pronouns (who, which, that, whose, where, when). They allow you to add information about a noun within the same sentence rather than using two separate sentences — a sign of grammatical fluency that IELTS examiners actively reward. This guide explains defining and non-defining relative clauses with IELTS examples and the grammar rules that distinguish them.
1Defining Relative Clauses
A defining (restrictive) relative clause identifies which specific person or thing is being discussed. It is essential to the meaning — removing it would change who or what is being referred to. No commas are used. Pronouns: 'who' for people, 'which' or 'that' for things, 'whose' for possession. Examples: 'The policy that the government introduced last year has reduced emissions by 15%.' ('that the government introduced last year' tells us which policy.) 'Students who choose to study abroad typically develop greater independence and cross-cultural awareness.' ('who choose to study abroad' identifies which students.) 'The country whose emissions are highest has the greatest responsibility to act.'
2Non-Defining Relative Clauses
A non-defining (non-restrictive) relative clause adds extra information about a noun that is already fully identified. Commas are required. 'That' cannot be used — only 'who' or 'which'. Examples: 'Renewable energy, which now accounts for 30% of global electricity generation, is expanding rapidly.' (The commas signal that 'which now accounts for…' is bonus information about renewable energy in general, not a specific subset.) 'Professor Liu, who has published over 100 peer-reviewed articles, will lead the research team.' (We already know which professor — the clause adds information.) Non-defining relative clauses are a hallmark of sophisticated written English and appear frequently in academic texts — using them correctly in Task 2 signals Band 7+ grammatical control.
3Reduced Relative Clauses
Relative clauses can be 'reduced' by omitting the relative pronoun and auxiliary verb, creating a participial phrase. Active reduced: 'The students who are studying abroad…' → 'The students studying abroad…'. Passive reduced: 'The research which was published in 2022…' → 'The research published in 2022…'. Reduced relative clauses are more economical and are characteristic of formal academic writing. Example in context: 'The measures implemented by the government, while well-intentioned, have failed to achieve their stated objectives.' (Full form: 'The measures that were implemented by the government…'). Using both full and reduced forms in the same essay demonstrates grammatical range.
4Common Errors to Avoid
Error 1 — Using 'that' in non-defining clauses: 'Social media, that has transformed communication, raises privacy concerns.' Fix: use 'which'. Error 2 — Double subject: 'The government they introduced a new policy.' Fix: 'The government introduced…' or 'The government, which introduced…'. Error 3 — Wrong comma placement: 'The report, that analysed 50 countries showed…' — if using 'that', no comma. If comma, use 'which'. Error 4 — Using 'who' for things: 'The law who was passed in 2020…' Fix: 'The law that/which was passed in 2020.' Error 5 — Omitting comma in non-defining clause: 'Professor Liu who has published 100 articles will lead the team.' Non-defining clauses must be enclosed by commas.
🎯 Key Takeaway
Relative clauses are an ideal target for grammatical improvement because they appear in almost every paragraph of academic writing. Practise by taking three sentences from your last Task 2 essay and converting each one to include a defining or non-defining relative clause. Review for comma rules and pronoun choice.