What is relative clauses in English grammar?

Relative Clauses is an important concept in English grammar. This lesson explains the rules, formation, and usage with clear examples to help you master it.

How do I use relative clauses correctly?

To use relative clauses correctly, follow the rules explained in this lesson. Pay attention to the examples and practice with the quiz at the end of the page.

What are common mistakes with relative clauses?

Common mistakes include incorrect formation and usage in context. Review the examples in this lesson to avoid these errors in your writing and speaking.

Clauses

Relative Clauses

Quick Summary

Relative clauses add information about nouns using pronouns like who, which, that, whose, and where. Defining clauses (no commas) identify which one; non-defining clauses (with commas) add extra information about something already identified.

Relative clauses are clauses that give additional information about a noun in the main sentence. They begin with relative pronouns (who, whom, whose, which, that) or relative adverbs (where, when, why). Understanding relative clauses is essential for creating sophisticated, flowing sentences and avoiding choppy writing.

Relative Pronouns Overview

Pronoun	Used For	Function	Example
who	people	subject	The woman who called is here.
whom	people	object (formal)	The man whom I met was kind.
whose	people/things	possession	The artist whose work I admire...
which	things/animals	subject/object	The book which I bought...
that	people/things	subject/object	The car that he drives...
where	places	location	The city where I was born...
when	time	time reference	The day when we met...
why	reasons	reason	The reason why I left...

Defining (Restrictive) Clauses

Defining clauses give essential information that identifies which person or thing we're talking about. Without this information, the sentence would have a different meaning or be unclear. No commas are used.

The man who lives next door is a doctor. (Which man? The one who lives next door.)
The book that you recommended was excellent. (Which book? The one you recommended.)
Students who study hard usually succeed. (Which students? Those who study hard.)
The restaurant where we had dinner is closing. (Which restaurant? Where we had dinner.)
I need a car that is reliable. (What kind of car? A reliable one.)

Non-Defining (Non-Restrictive) Clauses

Non-defining clauses give extra information about something already identified or unique. The main meaning is clear without this information. Always use commas.

My brother, who is an engineer, lives in London. (I only have one brother; his profession is extra info.)
Paris, which is the capital of France, is beautiful. (Paris is already identified; the extra info isn't essential.)
Einstein, who developed relativity, was brilliant. (Einstein is already known.)
My car, which I bought last year, broke down. (I only have one car.)
She gave me the book, which I had been wanting to read. (The book has been specified already.)

⚠️ Commas Change Meaning!

No commas (defining): "The students who passed the exam can leave."
→ Only the students who passed can leave. (Others must stay.)

With commas (non-defining): "The students, who passed the exam, can leave."
→ All students passed, and all can leave. (Extra info.)

That vs. Which

Understanding when to use "that" vs. "which" is important, especially in American English:

That = defining clauses (no commas): "The car that I bought is blue."
Which = non-defining clauses (with commas): "My car, which I bought last year, is blue."
Which can also be used in defining clauses (more common in British English): "The car which I bought is blue."
That is NEVER used in non-defining clauses: "My car, that I bought last year..." ❌

Who vs. Whom

"Who" is a subject pronoun; "whom" is an object pronoun. While "whom" is becoming less common in everyday speech, it's still preferred in formal writing.

The teacher who taught me English was excellent. (WHO = subject of 'taught')
The teacher whom I admire has retired. (WHOM = object of 'admire'; formal)
The teacher who I admire has retired. (WHO replacing whom; informal but acceptable)
To whom it may concern... (WHOM after preposition; formal)

💡 Who/Whom Test

Replace with he/him. If "he" works → use "who." If "him" works → use "whom."

"The man who/whom I met" → "I met him" → use "whom"

"The man who/whom called" → "He called" → use "who"

Whose (Possession)

"Whose" shows possession and can refer to people or things (despite what some traditional guides say).

She's the artist whose paintings sell for millions.
I know a man whose wife is a famous actress.
The company whose products we use is based in Japan.
This is the house whose roof was damaged in the storm.

Where, When, Why (Relative Adverbs)

This is the restaurant where we first met. (place)
I remember the day when we graduated. (time)
Do you know the reason why she left? (reason)
The town where I grew up is very small.
That was the moment when everything changed.

Note: "That" often replaces "when" and "why": "the day that we met," "the reason that she left."

Omitting Relative Pronouns

In defining clauses, you can omit the relative pronoun when it's the object of the clause:

The book (that/which) I read was good. (Object: I read the book)
The man (who/whom) she married is Italian. (Object: she married the man)
The restaurant (that/where) we went to was expensive.

Cannot omit when it's the subject:

The man who lives here is nice. (NOT: The man lives here is nice.)
The book which is on the table is mine. (NOT: The book is on the table is mine.)

Prepositions with Relative Clauses

Prepositions can go at the end of the clause (informal) or before the pronoun (formal):

The person (who/that) I spoke to was helpful. (informal, end position)
The person to whom I spoke was helpful. (formal, before pronoun)
The house (which/that) we looked at was too expensive.
The house at which we looked was too expensive. (very formal)

Common Mistakes to Avoid

Using "that" in non-defining clauses: "My mother, that is a teacher,..." ❌ → "My mother, who is a teacher,..." ✓
Missing commas in non-defining clauses: "Paris which is beautiful..." ❌ → "Paris, which is beautiful,..." ✓
Adding commas to defining clauses: "Students, who study hard, succeed." ❌ (unless you mean ALL students study hard)
Wrong pronoun for things: "The book who I read..." ❌ → "The book that/which I read..." ✓
Omitting subject pronouns: "The man lives next door is nice." ❌ → "The man who lives next door is nice." ✓

Combining Sentences with Relative Clauses

Relative clauses help combine choppy sentences into smoother, more sophisticated writing:

Before: "I met a woman. She works at Google."

After: "I met a woman who works at Google."

Before: "Tokyo is Japan's capital. It has over 13 million people."

After: "Tokyo, which is Japan's capital, has over 13 million people."

Frequently Asked Questions

Can I use "that" for people?

Yes! "That" can refer to people in defining clauses: "The woman that called" is correct, though "who" is often preferred. In non-defining clauses, always use "who" for people.

How do I know if a clause is defining or non-defining?

Ask: "If I remove this clause, will readers know exactly what/who I mean?" If yes → non-defining (use commas). If the sentence becomes vague → defining (no commas).

Is "whom" dying out?

"Whom" is less common in everyday speech but still used in formal writing and after prepositions ("to whom," "for whom"). Using "who" as an object is widely accepted in informal contexts.

Can "whose" refer to things?

Yes! While "whose" traditionally referred only to people, it's now widely accepted for things: "The company whose products we sell" is correct. The alternative "of which" sounds very formal: "The company the products of which we sell."

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