Relative Pronouns (who/whom/which/that)

Here's a sentence you'd write in your English book without a second thought:

"The teacher who marked my essay is strict but fair."

No bother at all. Then you try something only slightly different — "The book who I borrowed…" — and the red pen appears. Or you freeze mid-story, wondering whether it's which or that, whether you need a comma, whether whom is something you're actually meant to use or just turns up in old books to sound posh.

Nobody's born knowing this. Relative pronouns look like tiny, unimportant words, but they're doing a very specific job: hooking one idea onto another so you don't have to keep starting fresh sentences. Once you can see that job clearly, the choices stop feeling like guesswork and start feeling like sense.

What a relative pronoun does

A relative pronoun introduces a relative clause — a mini add-on that tells you more about a noun that's just been mentioned. That earlier noun is called the **antecedent**.

"My cousin who lives in Cardiff is visiting next week."

Here cousin is the antecedent, who lives in Cardiff is the relative clause, and who links them. Without it, you'd need two separate sentences ("My cousin is visiting next week. She lives in Cardiff.").

The five main relative pronouns, and their usual jobs:

• who — for people, doing the action: "the girl who won the race."
• whom — for people, on the receiving end (there's a test for this below).
• whose — shows possession, for people or things: "the boy whose phone rang" / "the tree whose leaves fell."
• which — for animals and things: "the bus which left early."
• that — for people, animals or things, especially when the clause tells you which one you mean: "the film that I saw last night."

A quick test: turn the clause into its own mini-sentence, swapping the pronoun for he/she/it. "the girl who won the race" → "she won" → a person doing something → who. "the bus which broke down" → "it broke down" → a thing → which.

Restrictive vs non-restrictive — the split that changes everything

Some clauses are essential — you need them to know which person or thing is meant. These are restrictive (or defining), and they take no commas:

"Pupils who revise the night before tend to feel calmer in exams."

Not all pupils — only the ones who revise. Others are just bonus information: nice to know, but you'd still know who's meant without them. These are non-restrictive, and they sit between commas:

"My form tutor, who used to be an actor, runs our drama club."

I've only got one form tutor, so the actor bit is a bonus. This isn't just about looking neat — mixing it up changes what you're saying:

"Students who arrive late must report to reception." (only the latecomers) "Students, who arrive late, must report to reception." (this now claims all students arrive late — probably not what you meant!)

That vs which

In careful UK writing:

• Restrictive (essential, no commas): use that, or which without commas — "The novel that we studied last term is on the exam."
• Non-restrictive (extra, with commas): use which, always with commas — "The maths homework, which took three hours, was still unfinished by Sunday."

Both that and which turn up in restrictive clauses in everyday UK English, and neither is "wrong" there. But many teachers and exam boards prefer that, purely because it keeps the pattern crystal clear: that = essential, which + commas = bonus. That's a sensible habit for exam writing, even though real-world usage is more relaxed.

Who vs whom

Who is for the subject of the clause (the one doing the thing); whom is for the object (the one on the receiving end, or after a preposition). The test: rewrite the clause with he/she or him/her.

"the coach who yelled instructions" → "he yelled" → subject → who. "the coach whom the team trusted" → "the team trusted him" → object → whom.

Let's be honest — in speech and texts, almost nobody uses whom, and it's rarely noticed or minded. But in school essays and exam answers, using it correctly in the right spot still earns marks and signals control. And if whom feels stiff, or you're not sure it's right, you can often just drop the pronoun: "The teacher I spoke to was helpful" is completely correct and dodges the issue entirely.

Whose — for people and things

Whose shows possession, and it works perfectly well with things, not just people:

"The friend whose bag zip broke." / "The museum whose collection was stolen."

English doesn't have a smooth everyday alternative (the technically-possible "the museum the collection of which was stolen" sounds like it escaped from a Victorian novel), so whose quietly does the job for both. It's standard, not a mistake.

One thing we're not covering here: the mix-up between whose and **who's** — who's is short for "who is" or "who has." That who's/whose spelling trap is dealt with fully in [Whose vs Who's]; we're keeping this article to the pronoun choices themselves.

A couple of finer points

You can drop the relative pronoun when it's the object of a restrictive clause — "The song (that) we learned is stuck in my head" — but never when it's the subject ("The boy who lives next door…") and never in a non-restrictive clause. When the pronoun follows a preposition, formal writing sometimes moves it to the front — "the friend to whom I was talking" — while everyday English leaves it at the end: "the friend I was talking to." Both are correct. For more, see our guide to clauses in the Sentences pillar.

Quick check

1. Fill the gap: "The scientist ___ discovered the vaccine visited our school."

2. Add commas if needed (assume you have only one brother): "My brother who lives in Leeds is a nurse."

3. Choose that or which, and say whether the clause is restrictive: "I returned the phone ___ you left on the bus."

4. Is whom correct here? Fix it if not: "The player whom scored the winner."

5. True or false, and why: "Whose can only be used with people."

UK vs US Usage

The grammar is the same in UK and US English — what differs is house style. US guidance often draws a firmer line: that for restrictive clauses, which only for non-restrictive ones with commas. UK teaching is more relaxed about restrictive which without a comma, though plenty of UK mark schemes still like the cleaner that = restrictive pattern. Sitting a US-style exam? Stick to the strict rule. Whom is fading in speech on both sides but is still expected in formal writing, and whose for things is fully accepted. The pronouns themselves — who, whom, whose, which, that — don't change spelling; only the words around them do (colour / color).

Where next

• Pronouns: the foundations — personal, subject and object pronouns
• Possessive pronouns and determiners — background for whose
• Whose vs who's — the homophone trap — go there rather than re-learning it here
• Subordinators — how relative clauses fit among other subordinate clauses
• Sentence structure & clauses — the full architecture of relative clauses, reduced relatives, and free relatives, in the Sentences pillar.