eng8-4.3· Unit 4: Conditions & Connectors· ~13 min

Defining relative clauses: who/which/that

Identifying people and things.

A defining relative clause tells us which person or thing the speaker means — without it, the sentence loses its meaning. We use 'who' (or 'that') for people and 'which' (or 'that') for things, animals, and groups. There is NO comma before the clause because it is essential information: 'The boy who sits next to me is my friend' tells us exactly which boy. The relative pronoun can be the subject of the clause ('The dog that bit me was large') or the object ('The book that I read was interesting'). When the pronoun is the object, it can be left out entirely: 'The book I read was interesting.' 'Whose' shows possession ('the girl whose bag is red') and 'where' replaces a prepositional phrase of place — but these are introduced here only briefly. For example: 'The teacher who teaches us maths is very patient' — 'who teaches us maths' defines exactly which teacher, making 'who' compulsory here.

Key terms

Defining relative clause — A clause that tells us exactly which person or thing the speaker means. It gives essential information, so the sentence loses its meaning without it, and it takes no commas.
Relative pronoun — A word such as 'who', 'which', or 'that' that introduces a relative clause and links it to a noun. 'Whose' shows possession and 'where' refers to a place.
Antecedent — The noun that the relative clause describes. The relative pronoun must agree with it: 'who' for a person, 'which' for a thing or animal.
Subject relative pronoun — A relative pronoun that is the subject of its clause, as in 'The dog that bit me'. A subject pronoun cannot be omitted.
Object relative pronoun — A relative pronoun that is the object of its clause, as in 'The book that I read'. An object pronoun can be left out: 'The book I read'.
Non-defining relative clause — A clause that adds extra, non-essential information and is marked off by commas, as in 'Baku, which is the capital of Azerbaijan, is beautiful'. It is the opposite of a defining clause.
Relative pronouns
PronounRefers toExample
whopeopleThe woman who lives next door is a doctor.
whichthings or animalsThis is the book which I told you about.
thatpeople or things (defining clauses)The dog that bit the boy ran away.
Defining clause: usage rules
FeatureRuleExample
InformationGives essential information that identifies the nounThe boy who sits next to me is my friend.
CommasNever use a comma before a defining relative clauseThe girl who won the prize was very happy.
'that''that' can replace 'who' or 'which' in defining clausesThe man that arrived late apologised.
Object pronounAn object pronoun may be omittedThe film (that) we watched was great.
✎Join two sentences about a thing
  1. 1Sentences: I found a wallet. The wallet was lying on the stairs.
  2. 2Choose the pronoun: A wallet is a thing, so use 'that' (or 'which').
  3. 3Replace the repeated noun: Replace the second 'The wallet' with 'that' and attach the clause to the first sentence.
  4. 4Result: I found a wallet that was lying on the stairs. No comma is used, because the clause is essential.
✎Join two sentences about a person
  1. 1Sentences: There are many teachers at our school. One teacher helped me pass the exam.
  2. 2Choose the pronoun: A teacher is a person, so use 'who' (or 'that').
  3. 3Replace the repeated noun: Replace 'One teacher' with 'who' and join it to 'The teacher'.
  4. 4Result: The teacher who helped me pass the exam is very patient. With many teachers, the defining clause is needed to identify which one, so no commas are used.
🚫Common mistake

Use 'who' for people and 'which' for things or animals. Writing 'the teacher which explains grammar' is wrong; it should be 'the teacher who explains grammar'.

⚠️Caution

Defining relative clauses take NO commas. 'The girl, who won the prize, was very happy' turns it into a non-defining clause, implying there is only one girl.

🚫Common mistake

Do not repeat the subject pronoun. 'The man who he arrived' is wrong, because 'who' is already the subject; write 'The man who arrived'.

💡Note

'What' is never a relative pronoun after a noun. Use 'who', 'which', or 'that' instead of 'the book what I read'.

Rules

  1. 1Use 'who' or 'that' to introduce a defining relative clause about a person: 'the student who/that answered correctly'.
  2. 2Use 'which' or 'that' to introduce a defining relative clause about a thing or animal: 'the car which/that broke down'.
  3. 3Never use a comma before a defining relative clause — the clause is essential to identify the noun.
  4. 4When the relative pronoun is the object of the clause, it may be omitted: 'The film (that) we watched was great.'
  5. 5The relative pronoun must agree with its antecedent: 'who' → person, 'which' → thing; 'that' works for both but is slightly more informal.

Practice

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