Relative Clauses
Why This Matters
Read these two lines out loud:
“I have a friend. My friend can speak five languages.”
They are correct. But they sound choppy, like a small child speaking. Now read this:
“I have a friend who can speak five languages.”
Smoother, isn’t it? One smooth sentence instead of two short ones. That little word who did the magic. It joined the two ideas into one neat sentence. The part it added — who can speak five languages — is called a relative clause.
This is one of the most useful tools in English. Once you can use relative clauses, your writing stops sounding like a list of tiny sentences and starts sounding fluent. You need it for letters, essays, stories, answers — everywhere. And in Words and Expressions II, Unit 1 makes you practise it again and again. So let’s learn it properly, from zero.
The Big Idea
A relative clause is a group of words that describes a noun. It usually begins with a relative pronoun — who, whom, whose, which or that — and it lets you add information about that noun without starting a brand-new sentence.
That is the whole idea in two lines. Everything else in this unit is just the detail of which pronoun to pick and when to use commas. Before we go further, let’s make sure two old words are fresh in your mind.
This unit leans on words like noun, clause and pronoun from earlier classes. If any of them feel foggy, here is a quick refresher:
Let’s Break It Down
What a relative clause is (and the relative pronouns)
A relative clause sits right next to a noun and tells you more about it. Look at Figure 1.1 — it labels every part of a simple example so you can see exactly what is going on.
The picture below shows the relative clause boxed, with an arrow pointing to the noun it describes:
Notice three things. First, the clause comes right after the noun it describes (“boy”). Second, it begins with a relative pronoun (“who”). Third, the whole sentence is still one sentence — we did not have to write “He won the race” separately.
There are five relative pronouns you need for Class 10:
- who — for people (as the doer)
- whom — for people (as the receiver of the action)
- whose — for possession (something belongs to the person or thing)
- which — for animals and things
- that — for people or things, but only in defining clauses (more on that soon)
Why bother with relative clauses at all? Because without them, you would have to keep stopping and starting new sentences every time you want to add a detail. Relative clauses let you pack the extra detail neatly into the same sentence, so your writing flows. That flow is exactly what examiners reward.
Which pronoun to use — who / whom / whose / which / that
This is where students get stuck, so let’s make it simple. You only have to ask yourself a few questions in order. Figure 1.2 turns those questions into a decision tree you can follow every single time.
Here is the decision tree — follow it from the top, answering each question, until it lands you on a pronoun:
Let’s see each one with a tiny example:
- who (person, doer): The girl who sits next to me is from Assam. (The girl does the sitting.)
- whom (person, receiver): The teacher whom we met is very kind. (We met the teacher — the teacher is the one met.)
- whose (possession): The man whose car was stolen called the police. (The car belongs to the man.)
- which (thing/animal): The book which is on the table is mine. (A book is a thing.)
- that (person or thing, defining only): The phone that I bought is new. / The boy that scored a century is my cousin.
Why does “whom” exist as a separate word from “who”? English keeps a special form for when the person is the receiver of the action, not the doer. It is the same reason we say “he called me” and not “he called I” — the receiver of an action takes a different form. Figure 1.5 makes the doer-versus-receiver difference clear.
The two panels below show exactly when to use who and when to use whom:
A quick trick: if you can replace the gap with he/she/they, use who. If you would replace it with him/her/them, use whom. The man (he called me) → who. The man (I called him) → whom.
Choose the right pronoun: 'The doctor ___ treated my father is famous.' Should it be who or whom?
Defining vs non-defining clauses — and the comma rule
This is the part exams love most. There are two kinds of relative clause, and the only visible difference is commas. Figure 1.4 puts them side by side.
The card below compares the two kinds and shows the simple test that tells them apart:
Let’s slow down, because this is the heart of the unit.
A defining clause tells you which one. It picks out the exact noun you mean. Without it, the listener would not know who or what you are talking about. “The boy who broke the window ran away” — the clause “who broke the window” is the only thing that tells us which boy. It is essential, so it gets no commas.
A non-defining clause just adds extra information. You already know which noun is meant; the clause only tells you something more about it. “My brother, who lives in Delhi, is a doctor” — you already know which person (“my brother”), so “who lives in Delhi” is just a bonus fact. It is removable extra, so it gets commas around it.
Why does one take commas and the other doesn’t? Think of the commas as a pair of little handles that say “you can lift this part out”. Extra, removable information is wrapped in commas to mark it as “not essential — feel free to skip it”. But essential information is part of the noun’s meaning; you can’t lift it out, so there are no handles, no commas. The commas are a signal: defining (no commas) means “you need this to know which one”; non-defining (commas) means “this is just extra”.
There is one more rule that depends on this. You can use that only in defining clauses. “The book that I lost was new” is fine. But you can never say “My brother, that lives in Delhi, …” — non-defining clauses must use who/whom/whose/which, never that. Here is the same idea laid out as a table:
The comparison table below sums up the two types so you can revise them at a glance:
| Feature | Defining clause | Non-defining clause |
|---|---|---|
| What it does | Tells you WHICH one — essential | Adds extra info — removable |
| Commas? | No commas | Yes — commas around the clause |
| Removable test | Remove it and the meaning is lost | Remove it and the sentence still makes sense |
| Can use 'that'? | Yes (who/which/that all allowed) | No — never use 'that' |
| Example | The man who phoned is my uncle. | Mr Rao, who phoned, is my uncle. |
Joining two sentences into one with a relative clause
Now the skill the unit tests most: take two short sentences that share a noun, and join them into one using a relative clause. Figure 1.3 shows the three steps you follow every time.
The flow below walks through joining two sentences, step by step:
The method is always the same three steps:
- Find the noun that appears in both sentences.
- In the second sentence, replace that repeated noun with the right relative pronoun (use Figure 1.2 to choose).
- Slot that clause in right after the noun in the first sentence.
Let’s do one together, carefully.
Join these two sentences using a relative clause: (1) This is the house. (2) Gandhi lived in the house.
- Find the shared noun. Both sentences mention “the house”. That is our link word.
- Decide the pronoun. “House” is a thing, not a person. So from Figure 1.2 we pick which (or that).
- Replace the repeated noun in sentence 2. Sentence 2 is “Gandhi lived in the house.” The house is a thing the action happens in, so we keep the little word “in”: “in which Gandhi lived” — or, more naturally, “which Gandhi lived in”.
- Attach it after the noun in sentence 1. Final answer: This is the house which Gandhi lived in. (You could also write the neater, formal version: This is the house in which Gandhi lived.)
Now one with a person, where you must choose between who and whom.
Join these two sentences: (1) The author won a prize. (2) I admire the author.
- Find the shared noun. “The author” appears in both. That is the link.
- Person or thing? A person. So the pronoun is who or whom.
- Doer or receiver? In sentence 2, “I admire the author”, I do the admiring and the author receives it. The author is the receiver (object). Test: “I admire him” → him means we use whom.
- Build it. Replace “the author” in sentence 2 with whom, then attach after the noun in sentence 1. Final answer: The author whom I admire won a prize.
And one non-defining join, where commas are needed.
Join into ONE sentence, keeping the second idea as extra information: (1) My grandmother is 80 years old. (2) My grandmother still climbs stairs easily.
- Shared noun: “my grandmother”, in both sentences.
- Essential or extra? We already know exactly who we mean — my grandmother. There is only one. So the second fact is extra information, not something needed to identify her. That means a non-defining clause — with commas.
- Pronoun: a person, the doer (“she still climbs”) → who. Remember: non-defining clauses can never use “that”.
- Wrap the clause in commas and slot it in. Final answer: My grandmother, who is 80 years old, still climbs stairs easily.
Common Mistakes
These are the traps students fall into again and again. Read each “Why it seems right” to spot the lure, then the “Actually” to fix it.
Using 'which' for a person, like 'The man which helped me was kind.'
In Hindi and other home languages, one all-purpose word often covers both people and things, so it feels natural to use one word ('which') for everything in English too.
Use 'who' (or 'whom'/'that') for people, and keep 'which' only for animals and things. The correct sentence is 'The man who helped me was kind.'
Putting commas around a defining clause, like 'The boy, who broke the window, ran away.'
Commas feel like a natural pause when you speak, and students sprinkle them wherever they would take a breath, so adding them around the clause feels safe and tidy.
A defining clause takes NO commas, because it is essential — it tells you which boy. Commas are only for non-defining (extra, removable) clauses. Write 'The boy who broke the window ran away.'
Using 'that' in a non-defining clause, like 'Mumbai, that is on the coast, is crowded.'
'That' works so smoothly in defining clauses ('the city that I love') that students assume it must work everywhere a relative pronoun is needed.
'That' is allowed only in defining clauses (no commas). A non-defining clause must use who/whom/whose/which. Write 'Mumbai, which is on the coast, is crowded.'
Repeating the noun or pronoun inside the clause, like 'The girl who she sings well is my friend.'
When you join two sentences, the second one originally had its own subject ('she'), so it feels right to keep it — you don't notice that the relative pronoun has already taken its place.
The relative pronoun REPLACES the repeated word — it does not sit beside it. Drop the extra 'she': 'The girl who sings well is my friend.'
Quick Check
Try these before moving on. Pick an answer, then read the explanation either way — it teaches the point.
Which sentence uses the relative pronoun correctly?
Fill the gap: 'The lady ___ bag was stolen filed a complaint.'
Which sentence has the commas right?
Choose who or whom: 'The friend ___ I trust most lives abroad.'
Practice Problems
Easy
Fill in the blank with the correct relative pronoun, then check the model answer.
Fill the gap: 'This is the dog ___ bit the postman.'
Answer: that (or which). A dog is an animal/thing, and the clause ”___ bit the postman” is essential (it tells us which dog), so it is defining. Both that and which are correct here: “This is the dog that bit the postman.”
Fill the gap: 'I thanked the man ___ helped me carry my bags.'
Answer: who (or that). “Man” is a person and he is the doer (he helped). Doer → who. “I thanked the man who helped me carry my bags.”
Fill the gap: 'The student ___ project won first prize is in my class.'
Answer: whose. The project belongs to the student — possession → whose. “The student whose project won first prize is in my class.”
Medium
Join each pair of sentences into one, using a relative clause.
Join: (1) I read a book last week. (2) The book changed my thinking.
Steps: Shared noun = “book” (a thing → which/that). It is defining (tells which book), so no commas. Replace “the book” in sentence 2 with “which/that” and attach after “book” in sentence 1.
Model answer: I read a book last week which changed my thinking. (Or: The book which I read last week changed my thinking.)
Join: (1) The scientist gave a talk. (2) We had invited the scientist.
Steps: Shared noun = “the scientist” (person). In sentence 2, we invited the scientist — the scientist is the receiver (object), so use whom. Defining clause → no commas.
Model answer: The scientist whom we had invited gave a talk.
Join as a NON-defining sentence (extra info): (1) Mr Khan teaches us maths. (2) Mr Khan has won a national award.
Steps: “Mr Khan” names one exact person, so the second fact is extra → non-defining → commas, and never “that”. He is the doer (he has won) → who.
Model answer: Mr Khan, who has won a national award, teaches us maths. (Or: Mr Khan, who teaches us maths, has won a national award.)
Challenge
Find and correct the error in each sentence, and say why.
Correct the error: 'The girl which is wearing a red dress is my sister.'
Error: “which” is used for a person. A girl is a person, so we need who (or that).
Correct sentence: The girl who is wearing a red dress is my sister.
Why: ‘which’ is only for animals and things; people take who/whom/whose/that.
Correct the error: 'My uncle who lives in Canada is visiting us next month.' (He is my only uncle, and this is extra information about him.)
Error: the clause is non-defining (we already know which uncle — he is the only one, and the fact is just extra), but it has no commas.
Correct sentence: My uncle, who lives in Canada, is visiting us next month.
Why: non-defining (removable, extra) clauses must be wrapped in commas. Test: drop the clause and “My uncle is visiting us next month” still makes full sense — that confirms it is extra information, so commas are needed.
Correct the error: 'The house, that we bought last year, is being painted.'
Error: two problems. First, “that” can never be used in a clause with commas (a non-defining clause). Second, this clause is actually defining — “that we bought last year” tells us which house, so it should have no commas at all.
Correct sentence: The house that we bought last year is being painted. (Or which, also fine: The house which we bought last year is being painted.)
Why: a defining clause is essential and takes no commas; and ‘that’ is only allowed in defining clauses anyway.
Summary
Here is everything you should now be able to do:
- Spot a relative clause — a group of words that describes a noun and begins with a relative pronoun (who, whom, whose, which, that). See Figure 1.1.
- Pick the right pronoun using the decision tree in Figure 1.2: person + doer → who; person + receiver → whom; possession → whose; thing → which; person or thing in a defining clause → that.
- Tell who from whom (Figure 1.5): if you’d say “he/she”, use who; if you’d say “him/her”, use whom.
- Use commas correctly (Figure 1.4): a defining clause is essential and takes no commas; a non-defining clause is extra and takes commas. The removable test decides it: if you can drop the clause and still know which noun is meant, use commas.
- Never use ‘that’ in a non-defining (comma) clause, and never repeat the noun or its pronoun inside the clause.
- Join two sentences into one (Figure 1.3): find the shared noun, replace it in the second sentence with the right pronoun, and slot the clause in after the noun in the first.
What’s Next
You now know how to add neat, flowing detail to your sentences with relative clauses. In Unit 2: Articles, we will go even smaller — to the three tiniest but trickiest words in English: a, an and the. They look simple, but knowing exactly when to use each one (and when to use none at all) is something even strong students get wrong. We will sort it out, with clear rules and pictures, just like we did here.
Frequently Asked Questions
What is a relative clause and how does it work in a sentence?
A relative clause is a group of words that describes a noun. It begins with a relative pronoun (who, whom, whose, which, or that) and adds information about the noun without starting a new sentence. For example, 'I have a friend who can speak five languages' — 'who can speak five languages' is the relative clause describing 'friend'.
When do I use 'who' and when do I use 'which' in a relative clause?
Use 'who' (and 'whom'/'whose') when the noun you are describing is a person. Use 'which' when the noun is a thing or an animal. For example: 'The teacher who helped me' (person) and 'The book which I borrowed' (thing).
What is the difference between 'that' and 'which' in a relative clause?
'That' is used in defining (restrictive) relative clauses — the ones that are essential to identify the noun, with no commas. 'Which' is used in non-defining (non-restrictive) clauses — extra information set off by commas. For example: 'The car that I bought is red' (defining) vs 'My car, which I bought last year, is red' (non-defining).
What is the difference between a defining and a non-defining relative clause?
A defining clause tells us exactly which noun we mean — remove it and the sentence loses its meaning. A non-defining clause adds extra information about a noun that is already clear — remove it and the sentence still makes complete sense. Non-defining clauses are set off by commas; defining ones have no commas.
What is the most common mistake students make with relative clauses?
The most common mistake is using a relative pronoun for people ('who') when referring to a thing, or forgetting commas in a non-defining clause. Another frequent error is doubling the pronoun — writing 'The girl who she sits next to me' instead of 'The girl who sits next to me' (drop 'she' because 'who' already does that job).