Learning objectives
- Use 'who' correctly to refer to people as the subject of a relative clause
- Use 'which' and 'that' correctly to refer to things
- Use 'whom' correctly to refer to people as the object of a relative clause
- Use 'whose' to express possession within a relative clause
- Use 'where' and 'when' to refer to places and times
- Distinguish defining (restrictive) from non-defining (non-restrictive) relative clauses
- Apply the comma rule correctly and know that 'that' cannot be used in non-defining clauses
Grammar & vocabulary
The relative pronouns
who = people, as the subject of the clause: "The man who called is my uncle." which = things, as subject or object: "The book that/which I read was great." that = people or things, defining clauses only: "The book that I read was great." whom = people, as the object of the clause, more formal than 'who': "The woman whom I met is a doctor." ('who' is very commonly used instead of 'whom' as an object in informal English, but 'whom' is the formally correct form.) whose = possession, for people or things: "The student whose essay won the prize is here." where = place: "This is the house where I grew up." when = time: "That was the year when we met."
Defining (restrictive) relative clauses
A defining relative clause gives essential information that identifies exactly who or what is being talked about — without it, the sentence would be unclear or incomplete. Defining clauses use no commas. "The student who forgot his homework was punished." (identifies which student, out of many) "The book that I read was great." (identifies which book) "This is the house where I grew up." (identifies which house)
Non-defining (non-restrictive) relative clauses
A non-defining relative clause adds extra information about someone or something that is already fully identified — the sentence would still make complete sense without it. Non-defining clauses are always set off by commas, and crucially, 'that' cannot be used in them — only 'who', 'which', 'whose', 'where', or 'when'. "My brother, who lives in Paris, is visiting next week." (you have one brother; the clause just adds extra information) "Marrakech, which is a popular tourist city, attracts millions of visitors every year." (Marrakech is already identified by name)
Defining vs. non-defining: the comma rule in practice
Compare: "The brother who lives in Paris is visiting." (defining — no commas — this implies you have more than one brother, and the clause specifies which one) vs. "My brother, who lives in Paris, is visiting." (non-defining — commas — this implies you have only one brother, and the clause is extra, non-essential information). This is the single most important, most commonly tested point in this unit: the presence or absence of commas actually changes the meaning of the sentence, not just its punctuation.
Common mistakes
Using 'that' in a non-defining relative clause — 'My brother, that lives in Paris, is visiting' is incorrect; 'that' is only used in defining clauses, so the correct form is 'My brother, who lives in Paris, is visiting.'
Forgetting the commas around a non-defining relative clause — 'My sister who is a doctor lives in Rabat' (no commas) wrongly implies you have more than one sister and are specifying which one; if you only have one sister, it must be 'My sister, who is a doctor, lives in Rabat.'
Adding commas around a defining relative clause — 'The student, who forgot his homework, was punished' wrongly suggests there is only one student in the context and the clause is just extra information; if the clause identifies which student, it must have no commas: 'The student who forgot his homework was punished.'
Using 'which' to refer to a person — 'The teacher which helped me' is incorrect; 'which' only refers to things, so the correct form is 'The teacher who helped me.'
Omitting 'whose' and using 'who's' instead — 'who's' is a contraction of 'who is' or 'who has,' not a possessive; the possessive relative pronoun is 'whose': 'The student whose essay won the prize is here,' not 'The student who's essay won the prize.'
Worked example — Introducing a family
Passage
"Let me introduce my family. My mother, who works as a doctor, is originally from Fes — the city where she grew up. I also have two brothers: the brother who studies engineering lives with us, while the brother who works abroad, whom I only see twice a year, is currently in Canada. My grandfather, whose stories about his youth I love hearing, still remembers the year when he first visited Casablanca."
Explanation
"My mother, who works as a doctor," is non-defining (commas) because the speaker has only one mother — the clause is extra information. "the city where she grew up" uses 'where' for a place, defining, no commas needed since it directly follows and specifies 'Fes.' "the brother who studies engineering" and "the brother who works abroad" are both defining (no commas) because the speaker has two brothers, and each clause identifies which one. Inside the second, "whom I only see twice a year" is a separate non-defining clause (commas) adding extra detail about that already-identified brother. "My grandfather, whose stories..." is non-defining (commas, possession) since there is only one grandfather. "the year when he first visited" uses 'when' for time, defining, identifying which year.
3 practice exercises
Exercise 1
EasyChoose the correct relative pronoun (who, which, whose, where, when) for each sentence. 1) 'This is the house ___ I grew up.' 2) 'The scientist ___ discovered this theory won a Nobel Prize.' 3) 'That's the student ___ essay won the prize.' 4) 'I'll never forget the day ___ we graduated.'
Show answer
1) where (place) 2) who (person, subject) 3) whose (possession) 4) when (time).
Exercise 2
MediumDecide whether each sentence needs commas (non-defining) or not (defining), and add them where necessary. 1) 'My mother who is a teacher works at a local school.' (you have only one mother) 2) 'The book that I borrowed from the library is due tomorrow.' 3) 'Marrakech which is a popular tourist city attracts millions of visitors every year.' 4) 'The players who scored the most goals were rewarded.' (there were several players, only some scored the most)
Show answer
1) Needs commas (non-defining, extra info about your only mother): 'My mother, who is a teacher, works at a local school.' 2) No commas (defining, identifies which book): 'The book that I borrowed from the library is due tomorrow.' 3) Needs commas (non-defining, Marrakech is already identified by name): 'Marrakech, which is a popular tourist city, attracts millions of visitors every year.' 4) No commas (defining, identifies which players): 'The players who scored the most goals were rewarded.'
Exercise 3
HardCombine each pair of sentences into one, using an appropriate relative clause (defining or non-defining, with correct punctuation). 1) 'I met a woman yesterday. She is a famous author.' (you know several women; this identifies which one) 2) 'My father works abroad. He is an engineer.' (you only have one father) 3) 'This is the school. I studied English there.'
Show answer
1) 'The woman whom/who I met yesterday is a famous author.' (defining, no commas — identifies which woman). 2) 'My father, who is an engineer, works abroad.' (non-defining, commas — extra info about your only father). 3) 'This is the school where I studied English.' (defining, no commas — identifies which school).
3 exercices, c'est un début.
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FAQ
What is the difference between defining and non-defining relative clauses?
A defining (restrictive) relative clause gives essential information needed to identify what or who is being talked about, and uses no commas: 'The man who called is my uncle.' A non-defining (non-restrictive) relative clause gives extra, non-essential information about something already identified, and is set off by commas: 'My brother, who lives in Paris, is visiting next week.'
Can 'that' be used in non-defining relative clauses?
No. 'That' can only be used in defining relative clauses ('The book that I read was great'). In non-defining relative clauses, only 'who', 'which', 'whose', 'where', or 'when' can be used, never 'that' — 'My brother, that lives in Paris, is visiting' is incorrect; it must be 'My brother, who lives in Paris, is visiting.'
When should 'whom' be used instead of 'who'?
'Whom' is the formally correct relative pronoun when referring to a person who is the object of the verb in the relative clause: 'The woman whom I met is a doctor.' In informal, everyday English, 'who' is very commonly used instead of 'whom' in this position ('The woman who I met is a doctor'), but 'whom' remains the correct, more formal choice, especially in writing.