Relative Clauses
Level B2–C2 · who/which/that/where; defining & non-defining
◎What you'll master
- Tell a defining clause (essential, no commas) from a non-defining one (extra, with commas).
- Pick the right pronoun: who, which, that, whose, where, when, why.
- Know why that can never follow a comma in a non-defining clause.
- Omit the relative pronoun when it is the object — the film (that) we saw.
- Avoid the classic errors: a doubled subject and which for people.
1What a relative clause does
A relative clause adds information about a noun. It usually begins with a relative pronoun (who, which, that, whose) or a relative adverb (where, when, why), and it comes right after the noun it describes.
The key question is always: does the clause identify the noun, or just add extra detail? The answer decides whether you use commas — and even which pronouns are allowed.
2Choosing the pronoun
Match the pronoun to what the noun is — a person, a thing, a place, a time, a reason, or a possessor.
| Pronoun | Use it for… | Example |
|---|---|---|
| who | people (subject/object) | the man who called me |
| which | things & animals | the phone which I bought |
| that | people or things — defining only | the film that we saw |
| whose | possession | the artist whose work I love |
| where | a place | the café where we met |
| when | a time | the day when we arrived |
| why | a reason (after the reason) | the reason why he left |
3Defining vs non-defining
A defining clause is essential — remove it and you no longer know which person or thing is meant. A non-defining clause adds removable, extra information and is fenced off with commas.
| Defining (no commas) | Non-defining (commas) | |
|---|---|---|
| Meaning | identifies the noun | adds extra detail |
| Commas | none | around the clause |
| Can use that? | yes | no — who / which only |
| Can omit pronoun? | yes, if object | never |
| Example | My sister who lives in Rome is a chef. (I have several sisters) | My sister, who lives in Rome, is a chef. (I have one sister) |
Reading the commas
Non-defining commas change the meaning. My sister, who lives in Rome, is a chef says you have one sister and adds a fact. Without commas, who lives in Rome singles out one sister among several.
4Leaving out the pronoun
In a defining clause you can drop the relative pronoun when it is the object of the clause — that is, when another subject already follows it.
Object — you can omit it
Subject — you must keep it
The book I read was great. is correct because I is the subject after the noun. But The man lives here is nice. is wrong — a subject clause needs the man who lives here.
5The doubled-subject trap
The relative pronoun replaces the noun — it does not add to it. Once you have who as the subject, do not add another pronoun (he, she, they) to say the same thing again.
6Formal style: preposition + whom / which
In informal English a preposition usually drifts to the end: the person I spoke to. In formal writing it can move to the front, and it then takes whom (people) or which (things) — never that, and never a dropped pronoun.
This is the phone ______ I bought yesterday.
Which sentence is correct?______
I'll never forget the day ______ we arrived.
Which sentence punctuates the non-defining clause correctly?______
Which sentence is correct?______
The Eiffel Tower, ______ was built in 1889, is iconic.
Which sentence is correct?______
Choose the correct sentence.______
✎Fix the Error
Each sentence has one mistake in the underlined word. Type the correction and check.
1.the woman which lives next door
2.My brother who is a doctor lives in Rome.
3.the book what I read last week
4.the man who he called me yesterday
5.Paris, that is the capital of France, is beautiful.