What is the difference between who and whom?

Who is the subject form and whom is the object form. The climber who reached the ridge did the reaching; the climber whom we hired received the hiring. In everyday English, who covers both, except after a preposition at the front of the clause, where whom is still required: to whom it was sent.

When should I use that instead of which or who?

In defining clauses, that is the natural everyday choice for things and is also fine for people: the fuse that blew, the baker that kneaded the dough. Do not use that after a comma, in a non-defining clause. There, who or which is the only option.

Can whose refer to a thing, not only a person?

Yes. Whose works for people and for things: a rower whose boat leaked, a cottage whose roof needed work. Of which is a more formal alternative with things, but whose is standard in both speech and writing.

How is what different from which and that?

What is fused: it means the thing that, and it does not follow a named noun. What you packed will not fit has no noun before what. After a named noun you need which or that: the tools that were on the bench, never the tools what were on the bench.

Is it wrong to drop the relative pronoun?

Only when it is the object of a defining clause. The map I annotated is fine because the pronoun would have been the object of annotated. You cannot drop a subject pronoun: the fuse that blew cannot become the fuse blew if you still mean the clause. The omit-relative-pronoun page covers that choice in full.

English grammar · Intermediate

Relative Pronouns: Who, Whom, Which, That, Whose, and What

Written by Eleanor Whitfield, Lead English Curriculum Editor · Reviewed September 2026

Relative pronouns are the words that stand in for a noun inside a clause that describes it: who, whom, which, that, whose, and, in a fused clause, what. Each one tells you whether the noun is a person or a thing, whether it is the subject or the object of the clause, and whether possession is involved. Choosing the pronoun is a separate skill from building the whole relative clause.

The volunteer whose toolkit I borrowed is the one who repaired the kiln.

whose marks possession, who stands for the person as subject

What it is

A relative pronoun replaces a noun so that a second clause can describe it. Who and whom stand for people, which for things and animals, that for people or things in defining clauses, whose for possession, and what for a fused idea meaning the thing that. The pronoun has two jobs at once: it points back at the noun (the antecedent) and it plays a role inside the clause, as subject, object, or possessor. Get the role right and the choice of word follows.

The potter who glazed the bowls is the one whose kiln I used. (Who is the subject of glazed. Whose marks that the kiln belongs to the potter.)

How to spot it

Find who, whom, which, that, whose, or what right after a noun, or standing for a noun that is not repeated. Then ask what the word is doing inside its own clause: doing the verb (subject), receiving it (object), or marking ownership (whose).

the neighbour who feeds the cats (who is the subject of feeds)
the recipe that I ruined (that is the object of ruined)
the painter whose mural cracked (whose links the painter to the mural)
what you packed will not fit (what means the thing that you packed)

Whom is the object form of who. It is required after a preposition in formal style (to whom), but everyday English keeps who and puts the preposition at the end (who I spoke to).

Relative Pronouns Quick Reference

Which relative pronoun to choose

Pronoun	Stands for	Role in the clause	Typical example
who	people	subject, or object in everyday style	the guide who led the tour
whom	people	object, formal or after a preposition	the guide whom we hired; to whom it was sent
which	things and animals	subject or object	the ferry which left at dawn
that	people or things, defining clauses only	subject or object	the ferry that left at dawn
whose	people or things	possession	the potter whose kiln I used
what	a thing not named before (fused)	the thing that	what she baked cooled on the rack

Common Relative Pronouns Examples in English

Each pronoun grouped by the job it does, not by the type of clause around it:

People: Who and Whom

The climber who reached the ridge first waited for us.: who as subject of reached
She's the editor who everyone recommends.: who as object, everyday style
The candidate whom the board appointed starts in May.: whom as object, formal
To whom should I address the invoice?: whom required after a fronted preposition

In speech, who covers both subject and object. Keep whom for writing that already sounds formal, or for the slot after a preposition.

Things: Which and That

The kettle which boiled dry has a new fuse.: which as subject of boiled
This is the map that I annotated.: that as object of annotated
The owl which nested in the loft has gone.: which for an animal, subject
The glaze that cracked was too thick.: that as subject of cracked

In defining clauses, that is the everyday choice for things and is also fine for people. Which is required in non-defining clauses, which take commas.

Possession: Whose

I met a rower whose boat leaked.: the boat belongs to the rower
We stayed in a cottage whose roof needed work.: whose with a thing, not only a person
She's the chemist whose paper we cited.: whose plus a noun that is owned
A city whose harbour froze still had a market.: whose with a place treated as owner

Whose always needs a noun after it (whose boat, whose roof). Of which is a formal alternative for things: a cottage the roof of which needed work.

Fused What

What you measured was the wrong sample.: what = the thing that you measured
I packed what was left in the kiln.: what as object, no noun before it
What matters is the timing.: what as subject of the outer clause

What does not follow a noun. The man what called is not English; that clause needs who or that.

How Relative Pronouns Work

Five tests, in order: person or thing, subject or object, possession, defining or not, and whether what is fused.

Match the Pronoun to the Antecedent

The noun the clause describes is the antecedent. If it is a person, the pronoun is who, whom, that, or whose. If it is a thing or an animal, the pronoun is which, that, or whose. Mixing them is the error in the man which called and the book who I lost. That is the flexible everyday form in defining clauses, covering people and things alike.

the baker who kneaded the dough, the dough that she kneaded

who with a person, that with a thing

Person: who. Thing: which or that.

Subject Who, Object Whom (or Who)

Inside the clause, ask who is doing the verb. If the relative pronoun is the doer, it is the subject and the form is who (or that, or which). If it is the receiver, it is the object: whom in formal English, who in everyday English, or nothing at all when the pronoun is dropped. After a preposition that has moved to the front, whom is required: the person to whom I wrote.

the potter who fired the pots / the potter whom we hired

who does the firing, whom receives hired

Doing the verb: who. Receiving it: whom or who.

Whose Marks Possession, Not Who's

Whose is the possessive relative. It works for people and for things, and a noun must follow it. Who's is a contraction of who is or who has and never belongs in this slot. Of which can replace whose with things in a more formal style, but whose is standard in both speech and writing.

a workshop whose windows fog up

the windows belong to the workshop

Whose + noun. Never who's here.

That Stays in Defining Clauses

That is the default relative pronoun in defining clauses, the ones that identify the noun and take no commas. It cannot introduce a non-defining clause, the extra-information type that sits between commas: My kiln, which I bought second-hand, still works, never My kiln, that I bought second-hand. Who and which work in both types; that works in one.

the fuse that blew / my fuse, which blew yesterday, is cheap to replace

that in a defining clause, which in a non-defining one

Commas around the clause? Not that.

What Means The Thing That

What is a fused relative: it contains its own antecedent. What you packed means the thing that you packed, so there is no noun in front of it. It is not a substitute for which or that after a named noun. Use it when the thing has not been named and you want one word to do both jobs.

What the gauge showed surprised us.

what stands for the unnamed reading

No noun before what.

Common Mistakes with Relative Pronouns

Incorrect: The mechanic which serviced the van was late.

Correct: The mechanic who serviced the van was late.

Which does not stand for a person. Use who (or that in a defining clause). Which is for things and animals.

Incorrect: She's the potter who's kiln we borrowed.

Correct: She's the potter whose kiln we borrowed.

Who's means who is or who has. The possessive relative is whose, and it needs the owned noun right after it.

Incorrect: I packed the tools what were on the bench.

Correct: I packed the tools that were on the bench.

What cannot follow a named noun. After tools you need that or which. What would only work if the tools were unnamed: I packed what was on the bench.

Incorrect: My neighbour, that grows herbs, left a bunch on the step.

Correct: My neighbour, who grows herbs, left a bunch on the step.

That cannot open a non-defining clause, the extra-information type with commas. Who or which is required there.

Quick Check: Relative Pronouns

Choose who, whom, which, that, whose, or what for each gap.

1. The climber ___ reached the ridge first waited.

Answer: who (or that)

person as subject

2. To ___ should I send the invoice?

Answer: whom

object after a fronted preposition

3. We rented a cottage ___ roof leaked.

Answer: whose

possession, thing as owner

4. ___ you measured was the wrong sample.

Answer: What

fused: the thing that you measured

5. This is the map ___ I annotated.

Answer: that (or which, or nothing)

thing as object in a defining clause

Relative Pronouns FAQs

What is the difference between who and whom?: Who is the subject form and whom is the object form. The climber who reached the ridge did the reaching; the climber whom we hired received the hiring. In everyday English, who covers both, except after a preposition at the front of the clause, where whom is still required: to whom it was sent.
When should I use that instead of which or who?: In defining clauses, that is the natural everyday choice for things and is also fine for people: the fuse that blew, the baker that kneaded the dough. Do not use that after a comma, in a non-defining clause. There, who or which is the only option.
Can whose refer to a thing, not only a person?: Yes. Whose works for people and for things: a rower whose boat leaked, a cottage whose roof needed work. Of which is a more formal alternative with things, but whose is standard in both speech and writing.
How is what different from which and that?: What is fused: it means the thing that, and it does not follow a named noun. What you packed will not fit has no noun before what. After a named noun you need which or that: the tools that were on the bench, never the tools what were on the bench.
Is it wrong to drop the relative pronoun?: Only when it is the object of a defining clause. The map I annotated is fine because the pronoun would have been the object of annotated. You cannot drop a subject pronoun: the fuse that blew cannot become the fuse blew if you still mean the clause. The omit-relative-pronoun page covers that choice in full.