Relative pronouns — who, which, and that — are used to introduce relative clauses: parts of a sentence that give more information about a noun. Choosing the right relative pronoun and knowing whether to add commas are two of the most frequently tested areas of English grammar. Who refers to people, which refers to things, and that can refer to either — but with important restrictions. Understanding the difference between defining and non-defining relative clauses is essential for both accuracy and clarity in writing.
Before you start — think honestly about your own teaching and experience.
Look at the examples. Answer each question before reading the explanation — this is how your students will learn too.
Look at the words 'who', 'which', and 'that'. Each one introduces a clause that gives more information about a noun. What is different about the nouns they refer to?
'Who' refers to a person — 'the teacher'. 'Which' refers to a thing — 'the school'. 'That' refers to a person or thing — 'the book'. This is the basic selection rule. Who is for people. Which is for things. That can be used for either people or things but is more restricted — as the next discovery will show. These pronouns are called relative pronouns because they relate the extra information back to the noun they describe. The clause they introduce is a relative clause. Understanding which pronoun to choose — and when 'that' is appropriate — is the main challenge of this topic.
In Sentence A, the relative clause tells us which teacher — without it, we do not know which teacher the speaker means. In Sentence B, the teacher has already been identified ('my first teacher') — the relative clause just adds extra information. What do you notice about the punctuation?
Sentence A is a defining relative clause — it defines or identifies which person or thing is being talked about. Without it, the sentence is unclear. No commas are used. Sentence B is a non-defining relative clause — it adds extra information about someone already identified. It is separated from the main clause by commas and could be removed without losing the essential meaning. This distinction — defining (no commas, essential information) versus non-defining (commas, extra information) — is important for writing accuracy. 'That' is used in defining clauses only. It cannot be used in non-defining clauses. 'Who' and 'which' can be used in both, but commas signal the difference.
Non-defining (commas required, that NOT possible):
Mariam, who won the prize, was from Class 6.
The new textbook, which we received last term, is excellent.
Can you see why 'that' does not work in the non-defining clauses? What would happen if you removed the relative clause from each non-defining sentence?
In non-defining clauses, 'that' is not used — only 'who' (for people) and 'which' (for things). This is a clear rule with no exceptions in standard written English. The reason is partly historical and partly about register: non-defining clauses are more formal and more careful, and 'that' is considered too informal or too abrupt for these contexts. Removing the non-defining clause ('Mariam was from Class 6' / 'The new textbook is excellent') leaves a perfectly complete sentence — confirming that the information in the clause is extra, not essential. Removing the defining clause ('The student was from Class 6') leaves an incomplete, unclear sentence — confirming that the information is essential and defining.'
| Form | Use / Meaning | Example |
|---|---|---|
| Pronoun | Refers to | Defining or non-defining? |
| who | People | Both defining and non-defining |
| which | Things | Both defining and non-defining |
| that | People or things | Defining only — never non-defining |
| whose | People or things (possession) | Both defining and non-defining |
| where | Places (relative adverb) | Both defining and non-defining |
| when | Time (relative adverb) | Both defining and non-defining |
WHO VERSUS WHOM
Formal English distinguishes between 'who' (subject) and 'whom' (object) in relative clauses. 'The teacher who helped me' — 'who' is the subject of 'helped'. 'The teacher whom I thanked' — 'whom' is the object of 'thanked'. In everyday speech, 'who' is increasingly used in both positions, and 'whom' is mostly encountered in formal written English. At this level, it is enough to know that 'whom' exists as the object form and appears in formal texts. A useful test: if you can replace the relative pronoun with 'him' or 'her', use 'whom'. If you can replace it with 'he' or 'she', use 'who'.
OMITTING THE RELATIVE PRONOUN
In defining relative clauses, the relative pronoun can sometimes be omitted when it is the object of the clause — not the subject. 'The book (that) I borrowed was excellent.' — 'that' can be omitted because 'I' is the subject of 'borrowed'. However, when the relative pronoun is the subject of the clause, it cannot be omitted: 'The teacher who trained me' — 'who' cannot be dropped because it is the subject of 'trained'. In non-defining clauses, the relative pronoun can never be omitted.
RELATIVE CLAUSES IN FORMAL WRITING
Non-defining relative clauses, with their careful use of commas, are a feature of formal and academic writing. Teaching learners to use them accurately — with correct pronouns and correct punctuation — significantly improves the quality of their formal written work. Defining relative clauses are more common in both speech and writing and are slightly easier to teach because they have no comma requirement.
WHICH RELATIVE PRONOUN DO I NEED? - Does the noun refer to a person? → Who (or whom for object position in formal writing). - Does the noun refer to a thing? → Which. - Is it a defining clause and you want a neutral or informal option? → That (people or things). - Is it a non-defining clause (extra information, commas)? → Who or which only — never that. - Does it show possession? → Whose. - Does it refer to a place? → Where. To a time? → When. - Is there a comma before the relative pronoun? → The clause is non-defining — do not use that.
Choose the correct relative pronoun to complete each sentence.
Each sentence has one relative pronoun error. Write the correct sentence and explain the mistake.
Use this sequence directly in class — guided discovery, no textbook needed. Tap each step to mark it done.
STEP 1 — COMBINE TWO SENTENCES (7 minutes): Write pairs of sentences on the board. Ask learners to combine them into one sentence using the correct relative pronoun. For example: 'I know a teacher.' + 'She trained in Nairobi.' → 'I know a teacher who trained in Nairobi.' Do three or four examples together, then ask pairs to try their own. Focus on choosing who versus which based on whether the noun is a person or thing.
STEP 2 — COMMAS OR NO COMMAS? (8 minutes): Write four sentences — two defining (no commas), two non-defining (with commas). Ask learners: 'Can I remove the relative clause and still have a clear, complete sentence?' If yes, it is non-defining — add commas. If no, it is defining — no commas. Go through each sentence as a class. Then ask learners to write one of each type about their own school.
STEP 3 — THAT OR WHO/WHICH? (7 minutes): Write six sentences — three in defining clauses, three in non-defining clauses. Ask learners to decide: can 'that' be used here, or is 'who/which' required? Establish clearly: 'that' is possible in defining clauses, never in non-defining. Do any sentences contain commas? If yes, 'that' is automatically wrong.
STEP 4 — WHOSE, WHERE, WHEN (6 minutes): Introduce these three relative words briefly with clear examples. Ask learners to produce one sentence using each one. Focus on 'whose' for possession and 'where' for places — these are the most frequently needed beyond who/which/that. Correct any sentences where 'which' is used instead of 'where'.
STEP 5 — WRITE ABOUT YOUR SCHOOL (7 minutes): Ask learners to write five sentences about their school or teaching career using relative pronouns — at least one defining, one non-defining, and one using whose or where. Share with a partner for checking. Invite two or three to share with the class and provide specific feedback on pronoun choice and comma use.
Use directly in class — copy, adapt, or read aloud. No printing needed.
For each strategy, choose the option that best describes where you are now.
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