What are relative pronouns and their function?

Relative pronouns like who, which, and that introduce relative clauses, linking additional information to nouns in a sentence.

How do you choose between 'who' and 'whom'?

'Who' is used as the subject of a relative clause, while 'whom' is used as the object; for example, 'The teacher who taught me' vs. 'The teacher whom I admired.'

What is the difference between restrictive and non-restrictive relative clauses?

Restrictive relative clauses provide essential information about a noun, while non-restrictive clauses add extra information and are set off by commas.

Relative Pronouns: Who, Which, That, Whose

By the Dictionary Wiki Editorial Team · Published January 23, 2024 · Updated May 5, 2024 · 1,385 words · English Language

English often joins two related ideas into one sentence. Relative pronouns make that possible. Words such as who, whom, which, that, and whose point back to a noun and begin a clause that says more about it. They help you avoid repeating the same noun, make your writing less choppy, and add detail without starting a new sentence every time.

Relative Pronouns, Explained

A relative pronoun begins a relative clause, also known as an adjective clause. That clause describes or identifies a noun or pronoun from the main part of the sentence. The relative pronoun does two jobs at once: it stands in for the repeated noun, and it links the added clause to the sentence.

Without relative pronoun: I bought a laptop. The laptop has a cracked screen.

With relative pronoun: I bought a laptop that has a cracked screen.

Here, "that" refers back to "a laptop" and joins the two ideas neatly. This same basic pattern appears with all relative pronouns.

Main Relative Pronouns in English

Pronoun	Refers To	Role in the Clause
who	people	subject
whom	people	object
whose	people or things	possession
which	things/animals	subject or object
that	people or things	subject or object
where	places	location
when	times	time reference

Choosing Who or Whom

Who as the Subject

Who refers to people when the person is the subject of the relative clause. It takes the place of he, she, or they.

The nurse who checked my blood pressure was very kind.

Children who read every day often build stronger vocabularies.

The actor who won the award thanked his parents.

Whom as the Object

Whom also refers to people, but it acts as the object of the relative clause. It replaces him, her, or them. In everyday English, many speakers use "who" instead; "whom" sounds more formal.

The client whom we visited on Monday signed the contract. (formal)

The client who we visited on Monday signed the contract. (informal but acceptable)

He is the colleague with whom I shared an office. (very formal)

Tip: Try replacing the relative pronoun with he or him inside the clause. If he works, choose "who." If him works, choose "whom." For example: "We visited him on Monday" → "The client whom we visited."

How Which Works

Which is used for animals and things. It may be the subject of the relative clause, or it may be the object.

The phone which keeps freezing needs to be repaired. (subject)

The sofa which they ordered finally arrived. (object)

We found a puppy which had been hiding under the porch.

Which can also introduce a non-defining relative clause that comments on the whole idea before it:

The train was cancelled, which ruined our plans.

She finished the project early, which impressed her manager.

How to Use That

That is highly flexible. It can point to people or things, and it can work as either the subject or the object of the relative clause. Still, it cannot be used everywhere.

The jacket that I bought yesterday is too small. (thing, object)

The student that answered first got extra credit. (person, subject)

Have you returned the charger that you borrowed? (thing, object)

Key Rule: Use "that" only in defining relative clauses. Do not use it in non-defining clauses set off by commas.

✅ My cousin, who lives in London, is a doctor.

❌ My cousin, that lives in London, is a doctor.

Using Whose for Possession

Whose shows ownership or connection. It can replace his, her, its, or their, and it may refer to people, animals, or things.

The singer whose album topped the charts is touring in June.

We hired an engineer whose designs are used worldwide.

The tree whose branches touched the roof was trimmed.

The museum whose exhibits attract tourists is closed on Mondays.

Place and Time: Where and When

Where for Places

Where can stand in for "in which," "at which," or "to which" when the noun refers to a place.

The café where we met has changed owners.

This is the village where my grandparents lived.

The stadium where the final was played was completely full.

When for Times

When replaces expressions such as "in which" or "at which" when the noun refers to a time or period.

I still remember the morning when the results were announced.

Winter is the time when electricity bills usually rise.

There were moments when the room became completely silent.

Restrictive Relative Clauses

Defining relative clauses, also called restrictive clauses, give information needed to identify the person or thing being discussed. If you remove the clause, the meaning becomes incomplete or too vague. These clauses are not marked off with commas.

The cyclist who won the race broke the course record.

We need software that runs on older computers.

Employees who arrive early can choose their desks.

In defining clauses, English can use who, which, that, whose, where, and when. In American English, "that" is often chosen instead of "which" for defining clauses about things.

Extra-Information Relative Clauses

Non-defining relative clauses, also called non-restrictive clauses, add a side detail rather than identifying the noun. The main sentence would still be clear without them. These clauses are always separated by commas.

My uncle, who is 72, still cycles every weekend.

Tokyo, which is Japan's capital, has an enormous rail network.

Professor Lane, whose book won a prize, will speak tonight.

Critical Rule: Do not use "that" in non-defining clauses. Use who, whom, which, whose, where, or when instead.

Leaving the Relative Pronoun Out

You may leave out the relative pronoun when it is the object of a defining relative clause. If it is the subject, it must stay.

Object (can omit):

The recipe (that) I tried was surprisingly easy.

The consultant (whom) they hired starts next week.

Subject (cannot omit):

The recipe that uses fresh basil is my favorite. (cannot remove "that")

The consultant who called this morning left a number. (cannot remove "who")

In non-defining clauses, you can never drop the relative pronoun.

Errors to Watch For

Putting "That" in a Comma Clause

❌ Rome, that attracts millions of visitors, is very old.

✅ Rome, which attracts millions of visitors, is very old.

Choosing "Which" for a Person

❌ The doctor which treated my ankle was excellent.

✅ The doctor who treated my ankle was excellent.

Repeating the Subject by Accident

❌ The woman who she organized the event is my neighbor.

✅ The woman who organized the event is my neighbor.

Forgetting Commas Around Extra Information

❌ My brother who works in Madrid is an architect. (suggests I have more than one brother)

✅ My brother, who works in Madrid, is an architect. (I have one brother; the clause adds detail)

Try It Yourself

Fill in each blank with the best relative pronoun.

1. The boy _______ found the missing dog lives across the street.

Answer: who

2. The article _______ you shared was very helpful.

Answer: that / which

3. He is the professor _______ lectures fill the auditorium.

Answer: whose

4. The neighborhood _______ I grew up has changed a lot.

Answer: where

5. Do you remember the evening _______ the lights went out?

Answer: when

6. The manager _______ you need to contact is on the second floor.

Answer: whom / who

7. My bicycle, _______ is almost fifteen years old, still works well.

Answer: which

8. The volunteers _______ cleaned the park received certificates.

Answer: who / that

Relative pronouns let you connect details cleanly instead of stacking short, repetitive sentences. Once you know which forms refer to people, things, possession, places, and times, the next key step is punctuation: defining clauses do not use commas, while non-defining clauses do. Get those two habits right, and your sentences will sound clearer, smoother, and more natural.