A is a part of a sentence that gives more information about a noun, starting with who, which, that, whose, where or when. Use who for people, which for things, that for either in a defining clause, whose for possession and where for places. Non-defining clauses need commas.
What a relative clause does
A tells us which person or thing you mean, or adds extra information about them. It joins two ideas in one sentence, so your writing sounds more advanced and less choppy.
Two short sentences: I know a student. She speaks five languages. One sentence with a relative clause: I know a student who speaks five languages. The word who replaces she and joins the sentences.
- The man who lives next door is a doctor. · who for a person
- The report, which was published in March, shows rising costs. · extra information
Choosing the relative word
The word you choose depends on what it refers to.
- who: people. The teacher who helped me was very patient.
- which: things and animals. The laptop which I bought has a good battery.
- that: people or things, in defining clauses only. The book that I read was long.
- whose: possession, for people and things. She is a scientist whose research focuses on water.
- where: places. This is the town where I grew up.
- when: times. I remember the year when we moved house.
Defining and non-defining clauses
A defining clause is essential. Without it, we do not know which person or thing you mean. There are no commas: Students who revise regularly perform better. This means only the students who revise, not all students.
A non-defining clause adds extra information. The sentence is complete without it, so we put commas around it and we cannot use that: My brother, who lives in Canada, is a nurse. You have only one brother, so the clause is just extra.
Compare the two with care. Students, who work hard, pass exams means all students work hard. Students who work hard pass exams means only some of them do. Commas change the meaning.
Leaving out the relative word
In defining clauses, you can leave out who, which or that when it is the object of the clause, that is, when another subject follows it. The book I read was long. The people we met were friendly.
You cannot leave it out when it is the subject, that is, when a verb comes next. Say The student who won the prize studies engineering, not The student won the prize studies engineering.
Relative clauses with prepositions
In speech, the preposition usually goes at the end of the clause: The city I live in is crowded. In formal writing, you can move it before the pronoun and use which or whom: The city in which I live is crowded.
After a preposition, never use that or who: not the city in that I live.
A useful trick: which for a whole idea
A non-defining clause beginning with , which can refer to the whole idea before it. Many cities have introduced congestion charges, which has reduced traffic. This is a neat way to show a result in Task 2 without starting a new sentence.
Use it carefully. The comma is required, and the verb that follows is singular.
How to build one
To build a , start with two simple sentences about the same noun, then decide which one will become the extra information. Replace the repeated noun with who, which, whose or where, and put the new clause directly after the noun it describes. For example, I met a woman. She runs a language school becomes I met a woman who runs a language school. Repeat this with sentences of your own until the pattern feels natural, then try adding commas for extra information.
Common mistakes
Learners often repeat the subject or use the wrong word. These are the main ones to look for:
- The man who he lives next door is a doctor. Say: The man who lives next door is a doctor.
- The book that I read it was long. Say: The book that I read was long.
- Everything what she said was true. Say: Everything that she said was true.
- A teacher which helped me. Say: A teacher who helped me.
- My friend that lives in Spain, is a pilot. Say: My friend, who lives in Spain, is a pilot, or remove the comma and use that.
Who finds this hard?
- Japanese speakers: In Japanese the clause comes before the noun with no connecting word. In English it comes after the noun, so you need who, which or that to join it.
- Chinese speakers: Chinese also puts the clause before the noun. English clauses follow the noun and begin with a relative word, so practise building them after the noun.
- Korean speakers: Korean places the clause before the noun, as Japanese does. In English, put the noun first and then add who, which or that.
- Arabic speakers: Arabic often repeats a pronoun inside the clause (the book that I read it). In English the relative word already stands for that noun, so do not add the pronoun.
IELTS tip
are one of the clearest ways to show grammatical range in Writing Task 2. Aim for two or three accurate ones, such as people who work from home or a policy which has reduced traffic. Check the commas and make sure you do not repeat the subject.
Frequently asked questions
What is a relative clause?
It is a part of a sentence that describes a noun and begins with a word such as who, which, that, whose or where. It tells us which person or thing, or adds more information.
What is the difference between defining and non-defining clauses?
A defining clause is needed to know which person or thing is meant, and has no commas. A non-defining clause only adds extra information, has commas and cannot use that.
When can I leave out who, which or that?
You can leave it out when it is the object of the clause, meaning another subject follows it: the book I read. You cannot leave it out when it is the subject.
Should I use who or that for people?
Both are common in defining clauses, but who is more natural and slightly more formal for people. In non-defining clauses you must use who.
Sources
- Swan, M. (2016). Practical English Usage, 4th edition. Oxford University Press.
- Carter, R. and McCarthy, M. (2006). Cambridge Grammar of English. Cambridge University Press.