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, ten minutes later, you try something only slightly different — "The book who I borrowed…" — and the red pen appears. Or you're halfway through a story and you freeze, wondering whether it's which or that, whether you need a comma, whether "whom" is something you're actually meant to use or just something that turns up in old books to sound posh.

Nobody's born knowing this. And here's the thing — 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.

By the end of this, you'll be choosing between who, whom, whose, which, and that with real confidence — in homework, in stories, and in exams — and you'll know exactly when a rule is firm and when it genuinely bends.

Before you read on, here's where we're heading. By the end of this article, you'll be able to: - Explain what a relative pronoun does and pick the right one for people, things, and possession. - Tell restrictive clauses (essential information) apart from non-restrictive clauses (extra information) — and punctuate them correctly. - Choose confidently between that and which, and between who and whom. - Use whose even when the "owner" is a thing, not a person. - Recognise fancier patterns like pied-piping, and know where to go for the who's/whose trap (we won't re-teach it here).

Beginner (Foundation)

Let's start with the basic job these words do. 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, which is a fancy way of saying "the thing hanging in front of the clause."

Look at this:

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

• "cousin" is the antecedent.
• "who lives in Cardiff" is the relative clause.
• "who" is the relative pronoun linking them.

Without it, you'd need two separate sentences: "My cousin is visiting next week. She lives in Cardiff." The relative pronoun lets you fold the second idea straight into the first.

The five main relative pronouns, and their usual jobs:

• who — for people, when they're doing the action: "the girl who won the race."
• whom — for people, when they're on the receiving end of the action (we'll build a proper test for this later — don't worry about it yet).
• whose — shows possession, usually for people, but also for 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 is telling you which one you mean: "the film that I saw last night."

A quick test that helps: turn the relative clause into its own mini-sentence, replacing the pronoun with he, she, or it. "The girl who won the race" → "she won the race" → the person is doing something → who. "The bus which broke down" → "it broke down" → a thing doing something → which.

Here's something worth noticing early, because it'll matter a lot later: some relative clauses are essential — you need them to know which person or thing is meant. Others are just bonus information — nice to know, but not needed to work out who or what you're talking about. That difference controls commas, and it controls whether you reach for that or which. We'll unpack it properly in a moment. For now, just feel the difference:

"The girl who sits next to me in maths" — essential; tells you which girl.
"My best friend, who is hilarious," — extra; you already know who your best friend is.

Quick recap: - A relative pronoun hooks a describing clause onto a noun (the antecedent). - The core set: who, whom, whose, which, that. - Who/whom/whose are mostly for people; which is for things; that covers either when the clause is essential. - Some clauses are essential (identify which one); some are extra (add a bonus detail) — that split runs the whole rest of this article.

Intermediate (Development)

Restrictive vs non-restrictive — the split that changes everything

A restrictive (or defining) clause narrows down exactly which person or thing you mean. It's locked into the meaning of the sentence, and it takes no commas.

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

Not all pupils — only the ones who revise. Take the clause away and the sentence's claim changes completely.

A non-restrictive (or non-defining) clause adds extra information about someone or something you've already identified. It sits between commas (or after one comma, if it comes at the end of the sentence). You could delete it and the sentence would still know exactly who or what it means.

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

I've only got one form tutor. The bit about being an actor is a bonus fact — hence the commas.

Here's why this actually matters, beyond looking neat on the page: 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!)

Common Mistake:
Adding commas "for safety" around a clause that's actually essential.
✗ "That's the boy, who sits next to me."
✓ "That's the boy who sits next to me." (no commas — the clause tells us which boy)

That vs which — and the comma connection

In careful UK writing, this is the pattern that keeps you safe:

Non-restrictive clauses (extra, with commas): use which, always with commas.

"The maths homework, which took three hours, was still unfinished by Sunday."

Restrictive clauses (essential, no commas): use that, or which without commas.

"The homework that took three hours was maths."
"The novel which we studied last term is on the exam."

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 for restrictive clauses about things, purely because it keeps the pattern crystal clear: that = essential, which + commas = bonus. That's a sensible habit to build, especially for exam writing, even though real-world usage is more relaxed.

Who and whom in relative clauses

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 the one after a preposition.

The test: rewrite the clause as its own mini-sentence 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.
"The teacher to whom I gave the form" → "I gave the form to her" → whom.

Let's be honest — in speech, and in texts to friends, almost nobody uses "whom." People say "who" nearly everywhere, and it's rarely noticed or minded. But in school essays, competition entries, and formal exam answers, using "whom" correctly in the right spot still earns marks and signals control. Learning the he/him test means you get to choose on purpose, rather than guessing and hoping.

Pro-Tip:
If "whom" feels stiff or you're not sure it's right, you can often just drop the pronoun altogether: "The teacher I spoke to was helpful" is completely correct and dodges the issue entirely.

Whose — for people and for things

Whose shows possession:

"The friend whose bag zip broke."
"The school whose roof was repaired."

Yes — whose works perfectly well with things, not just people. "The museum whose collection was stolen," "a novel whose ending shocked everyone." English doesn't have a smooth everyday alternative for this (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 people and things. It's standard, not a mistake.

One thing we're not covering here: the mix-up between whose and who's. That's a spelling and homophone trap — who's is short for "who is" or "who has" — and it's dealt with fully in [H2.4: Whose vs Who's]. Go there for the drills; we're keeping this article to the pronoun choices themselves.

Quick recap: - Restrictive = essential, no commas; non-restrictive = extra, with commas — and mixing them up changes meaning. - Restrictive clauses about things: that, or which without commas. Non-restrictive: which, always with commas. - Who = subject, whom = object — test it with he/him or she/her. - Whose works for things as well as people. - The who's/whose spelling trap lives in H2.4 — not re-taught here.

Advanced (Mastery)

Pied-piping (yes, that's really its name)

When a relative pronoun is the object of a preposition, English gives you two options.

Stranding — leaving the preposition at the end, which is how most people actually talk:

"The friend I was talking to" → "the friend who(m) I was talking to."

Pied-piping — dragging the preposition to the front, along with the relative pronoun:

"The friend to whom I was talking."

The name comes from the preposition following the relative pronoun the way the children followed the Pied Piper. Both are entirely grammatical. What changes is register — how formal the sentence sounds. A story narrator might happily write "the cell I escaped from"; a polished, careful essay might prefer "the cell from which I escaped." Neither is more "correct." They're different outfits for different occasions.

Pro-Tip:
Read a pied-piped sentence aloud. If it sounds like something a very serious barrister would say, that's fine for a formal essay — but don't feel obliged to write that way in a story or a text to a friend.

Dropping the relative pronoun

In restrictive clauses where the pronoun would be the object, you can often drop it entirely:

"The song (that) we learned is stuck in my head."
"The boy (who/whom) I sat next to moved schools."

You can't drop it when it's the subject of the clause:

✗ "The boy lives next door plays football with me."
✓ "The boy who lives next door plays football with me."

And you never drop it in a non-restrictive clause:

✓ "My sister, who trains every morning, ran a half-marathon."
✗ "My sister, trains every morning, ran a half-marathon."

That with people — and when to prefer who

That is grammatically fine for people in restrictive clauses: "the students that submitted early…" But plenty of careful writers, and plenty of examiners, still prefer who for people, simply because it reads warmer and more precise. Neither is "wrong" — but who is often the better stylistic choice when you're writing about human beings.

Edge cases worth knowing

• Collective nouns: "the team who won" focuses on the people in it; "the team which won" focuses on the team as a single unit. Both exist — just stay consistent within one piece of writing.
• Animals: pets often get who (especially in stories, where they're characters); wildlife documentaries tend to use which.
• "Of which" as an alternative to whose: "a system whose flaws are well known" is smoother than "a system the flaws of which are well known" — reach for whose unless you have a specific reason for the stiffer version.
• Stacking clauses: don't pile too many relative clauses onto one sentence. "The girl who lived next door who had a dog that bit the postman who…" is exhausting to read. Break it up.

When you're ready to go even further into how relative clauses sit inside more complex sentences — reduced relatives, free relatives, and how clauses nest inside one another — that's proper territory for the full Clauses pillar, coming soon to this library. This article deliberately stops at the pronoun choices and the restrictive/non-restrictive engine that drives them.

Common Mistake:
Punctuating a restrictive clause as if it were non-restrictive: "Students, who revise, do better." That literally claims all students revise and do better. Drop the commas for the meaning you actually want: "Students who revise do better."

Quick recap: - Pied-piping (to whom, in which) is formal; stranding the preposition at the end is natural and common. - You can drop the relative pronoun in restrictive object clauses, never in subject clauses or non-restrictive clauses. - That is grammatical for people, but who often reads warmer in careful writing. - Collective nouns, animals, and "of which" are style choices, not fixed rules — just stay consistent. - Heavy stacking of relative clauses is a sign to start a new sentence.

UK vs US Usage

The underlying grammar of relative pronouns is exactly the same in UK and US English. What differs is house style and how strictly the rules get enforced.

That vs which and commas. US school guidance — and many US style guides — often draw a firmer line: that for restrictive clauses, which only for non-restrictive clauses with commas, no exceptions. UK teaching and editing is more relaxed about restrictive which appearing without a comma, though plenty of UK mark schemes still like the cleaner that = restrictive pattern. If you're sitting an exam that follows US-style conventions, play it safe and stick to the strict rule. For UK-style writing, either restrictive option is generally accepted — just be consistent within one piece.

Whom. Fading from everyday speech on both sides of the Atlantic — a teenager in Bristol and one in Boston are equally likely to say "who did you give it to" rather than "to whom did you give it." Formal written English in both countries still expects it in the right spots, though.

Spelling nearby (not the pronouns themselves). You'll see UK colour, favourite, organise alongside US color, favorite, organize in the sentences around a relative clause — but who, whom, whose, which, and that don't change spelling between the two varieties.

Whose with things. Fully accepted on both sides — no dialect argument to have there.

Quick recap: - US style guides enforce the that/which split more strictly; UK usage is more relaxed about restrictive which. - Whom is declining in speech everywhere, but expected in formal writing in both varieties. - The relative pronouns themselves don't change spelling between UK and US English — only the style expectations around them do.

Key Takeaways

• Relative pronouns (who, whom, whose, which, that) attach a describing clause to a noun without needing a fresh sentence.
• Restrictive clauses (no commas) identify exactly which person or thing you mean; non-restrictive clauses (with commas) add extra, droppable detail.
• Who is the subject form, whom the object form — test with he/him or she/her.
• Whose works with things as well as people; the who's/whose spelling trap is a separate issue, covered in H2.4.
• Pied-piping ("to whom," "in which") is a formal option; stranding the preposition is natural everyday English.

Check Your Understanding

1. Fill the gap with the correct relative pronoun: "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."

Answer key

1. who — subject of "discovered."
2. Non-restrictive, so commas are needed: "My brother, who lives in Leeds, is a nurse."
3. that (restrictive — it identifies which phone; no commas).
4. Incorrect. "Whom" should be "who," since it's the subject of "scored": "The player who scored the winner."
5. False. Whose works with things as well as people — e.g. "This is the novel whose first chapter had everyone hooked."

Internal Links

• H2.1 — Pronouns: the foundations (personal, subject and object pronouns)
• H2.2 — Possessive pronouns and determiners (background for whose)
• H2.4 — Whose vs who's (the homophone trap — go there rather than re-learning it here)
• H7.2 — Subordinators (how relative clauses fit among other subordinate clauses)
• Forward link — the future Clauses pillar (full architecture of relative clauses, reduced relatives, and free relatives)

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