Non-Defining Relative Clauses

A non-defining relative clause gives extra, non-essential information about a noun. The sentence makes sense without it — but commas are obligatory. My colleague Anna, who has worked here for ten years, has just been promoted. Three rules separate non-defining from defining: only who and which are allowed (that is not); commas are always required; and which can refer to a whole preceding clause (She arrived on time, which surprised everyone). The quick test: if you can remove the clause and the sentence still makes sense, commas are required.

This worksheet drills B2 use of non-defining relative clauses through transformation, pronoun-choice, and comma-test tasks.

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What’s inside:

• Grammar Box with three key rules (who/which only, that forbidden, which can refer to a whole clause) and the comma test
• Defining vs non-defining: identify which type each sentence needs and add commas as appropriate
• Combining: merge two sentences into one with a non-defining clause, with appropriate commas
• Which referring to a whole clause production: write three sentences using which to comment on the previous statement
• Full Answer Key plus Teacher Notes on the comma test and B2-level register

Common mistakes addressed: that in non-defining clauses (My manager, that I mentioned, agreed), missing commas (My colleague Anna who has worked here for ten years has just been promoted), and confusion of which (refers to thing or clause) with what (means the thing that).

For: Adult and teenage learners (14+) at CEFR B2, in upper-intermediate classes, 1:1 lessons, or self-study. Non-defining relative clauses are a B2 syntactic marker tested in Cambridge B2 First (FCE) Writing assessment criteria. Part of the Relative Clauses collection — the natural sibling is Defining Relative Clauses, which sets up the essential-information counterpart practised here.