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Teaching Relative Clauses: Who, Which, That, and the Art of Adding Information

Relative clauses let students build complex sentences. Here's how to teach them without the defining/non-defining confusion.

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Matthew James Soldato

ESL Teacher & Founder of DrillKitMar 24, 2026

Why Relative Clauses Matter for Fluency

Without relative clauses, students speak in short, choppy sentences: 'I have a friend. She lives in London. She speaks three languages.' With relative clauses, they produce natural, flowing English: 'I have a friend who lives in London and speaks three languages.' Relative clauses are the glue that creates sentence complexity — and sentence complexity is what separates A2 speakers from B2 speakers in any assessment criteria. CEFR descriptors explicitly reference the ability to 'link sentences using connectors and relative clauses' as a B1-B2 competence. Yet many students reach B2 without confidently producing them because the rules seem complicated. They're not — the teaching approach usually is.

Start With Function, Not Terminology

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WHO = People

'The teacher who taught me English was amazing.' Students practice by describing people without saying their name: 'The person who sits next to me...' Classmates guess who they mean.

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WHICH/THAT = Things

'The book which/that I'm reading is excellent.' Practice with a 'What's in my bag?' activity: students describe objects using relative clauses without naming them.

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WHERE = Places

'The restaurant where we ate last night was expensive.' Students describe places from their life: 'The city where I grew up...' 'The school where I studied...'

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Teacher Tip

Skip the terminology entirely. Instead say: 'If the information is ESSENTIAL to know WHICH ONE I mean, no commas. If the information is EXTRA/BONUS, use commas.' Example: 'My sister who lives in Paris visited me' (I have multiple sisters — this identifies WHICH one). 'My sister, who lives in Paris, visited me' (I only have one sister — the Paris info is bonus). Most students only need defining relative clauses until B2+. Don't overwhelm B1 students with non-defining clauses.

Frequently Asked Questions

When should I teach relative clauses in ESL?

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Introduce basic defining relative clauses (who, which, that, where) at B1. Practice heavily at B1-B2. Introduce non-defining clauses (with commas) at B2. Contact clauses (omitting the relative pronoun: 'The book I read' instead of 'The book that I read') can be introduced at B1 receptively and B2 productively.

What is the difference between which and that?

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In defining relative clauses, 'which' and 'that' are interchangeable for things in most contexts. In non-defining relative clauses (with commas), only 'which' is correct, never 'that'. For teaching purposes at B1, tell students 'that' works everywhere for things and introduce the 'which' distinction at B2.

How do I practice relative clauses communicatively?

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Use definition games: 'Describe a word using a relative clause and classmates guess.' Example: 'It's a person who flies planes' (pilot). Use 'Find someone who' activities modified to require relative clause responses. Use picture descriptions where students combine information about people and objects.

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