Relative Clauses (Defining & Non-Defining)

Here's a moment almost every working adult has had. You're typing an email at 4:55 on a Friday:

Please send the report which the client needs tomorrow.

Then you pause, cursor hovering. Do I need commas in there? Is which even the right word — should it be that? And, more quietly: am I actually saying what I mean, or just what sounded roughly right?

Let's be honest — relative clauses are the bit of grammar most grown-ups half-remember from school and then wing in real writing. They package extra information around a noun, and they come in two genuinely different flavours. One flavour picks out which person or thing you mean. The other just adds a fact you could easily have left out. Get the flavour wrong and, depending on the day, you either collapse your own meaning or accidentally invent extra brothers, extra reports, or three versions of your line manager who don't exist.

Nobody's born knowing this. The good news is you don't need to re-sit Year 8 grammar to fix it. We're not re-teaching relative pronouns here — who, which, that, whose — that's Pillar 2's job, and it's already done properly. And we're not drilling the full comma rules for non-defining clauses either; those sit squarely in the Punctuation pillar, and I'd rather point you there than give you half the picture twice. What we'll do here is build a working sense of the two jobs a relative clause can do, so your emails, CVs, reports, and everyday messages land the way you actually intend.

Before you read on, here's where we're heading. By the end of this article, you'll be able to: - Recognise a relative clause and the noun it's attached to. - Separate defining (restrictive) from non-defining (non-restrictive) jobs, cleanly and confidently. - Use a simple remove-it test to check which type you've actually written. - Place relative clauses so your work writing says exactly what you mean.

Beginner (Foundation)

A relative clause is a dependent clause that modifies a noun — in plain terms, a mini-description hitching a ride after the thing it describes. It usually starts with a relative pronoun: who, which, that, whose, occasionally whom.

Take an example from ordinary life:

The flat that we viewed on Tuesday has gone under offer.

"That we viewed on Tuesday" narrows down which flat. Without it, "The flat has gone under offer" is close to useless — which flat, out of the six you looked at this month?

Another:

I'm meeting Sara, who runs the design team, after lunch.

"Who runs the design team" is extra colour about Sara. Take it away and the sentence still works perfectly well: you still know exactly who you're meeting.

Those two examples already show the two jobs at play:

1. Defining relative clause (also called restrictive): essential information that defines which person or thing you mean.
2. Non-defining relative clause (also called non-restrictive): non-essential information you could remove without losing the identification.

UK style guides tend to say defining/non-defining; American ones often say restrictive/non-restrictive. Same two functions wearing different name badges — I'll keep both in play throughout, because you'll meet both in the wild.

One foundation truth worth nailing down: relative clauses can't stand alone. "Who runs the design team" isn't a sentence on its own — it's a dependent clause (see 3.1 if the independent/dependent distinction still feels shaky). It needs a main clause to lean on.

Quick recap: - Relative clauses describe a noun, usually starting with who / which / that / whose. - Defining (restrictive) = essential "which one?" information. - Non-defining (non-restrictive) = useful extra you could remove. - They're dependent clauses — incomplete if left standing alone.

Intermediate (Development)

This is the working layer — the bit that sorts a fuzzy email from a clear one.

Defining clauses: the filter. A defining clause restricts the noun. Only certain members of the set count.

Staff who work from home on Fridays should update SharePoint by 10am.

Not all staff — only those working from home on Fridays. Remove the clause and you've quietly changed the instruction for everyone else in the office.

More workplace and everyday examples:

• The invoice that arrived last week still hasn't been paid.
• Candidates whose CVs exceed two pages are returned unread. (Harsh, but it happens — and it's defining.)
• Please use the entrance which faces the car park.

In defining clauses, British English is quite comfortable using that for things, and often for people too in informal writing; more formal prose leans towards who/which.

Non-defining clauses: the aside. A non-defining clause adds a remark about a noun we already identify clearly.

Our office manager, who has been here twelve years, is retiring in June.

There's one office manager. The twelve years is a nice detail, shone on afterwards — strip it out and the sentence still names the same person and delivers the same core news.

• Manchester, which is two hours from Bristol on a good day, is hosting the conference.
• The Q3 report, whose final figures landed late, needs a rewrite.

The remove-it test. Use this every single time you're unsure:

1. Delete the relative clause.
2. Read what's left.
3. Decide: meaning muddied, "which one?" left unanswered — that's defining. Still clear who or what you mean, core message intact — that's non-defining.

Try it:

Please reply to the email I sent yesterday.

Delete it: "Please reply to the email." Vague — which one? → Defining.

Thanks to Priya, who fixed the spreadsheet, we hit the deadline.

Delete it: "Thanks to Priya, we hit the deadline." Still perfectly clear. → Non-defining.

Position: stick to the noun. Relative clauses belong right next to the thing they modify. Drift away from that and you get accidental comedy — or, at work, actual chaos:

We sent the proposal to the client with 14 pages of pricing.

Fourteen pages of client? Fix it:

We sent the proposal that has 14 pages of pricing to the client.

Misplaced modifiers get the full treatment at 5.3; the principle here is simple enough — glue the clause to the right noun and don't let it wander.

Where we're deliberately drawing a line. Punctuation for non-defining clauses — the commas that usually bracket them — belongs in the Punctuation pillar. Know that the commas exist; learn the precision of exactly where they go over there. And full pronoun selection (who vs whom, the that/which debate in detail) belongs back in Pillar 2's Relative Pronouns article. I'm not skipping those because they're unimportant — I'm skipping them because someone else already owns the job properly.

Common Mistake: Accidentally defining when you meant to add colour — or inventing extras you didn't intend. My brother who lives in Leeds is a solicitor quietly implies more than one brother. My brother, who lives in Leeds, is a solicitor rests on one brother, with Leeds riding along as an aside. In workplace bios, CVs, and introductions, this distinction matters more than people think.

Pro-Tip: In a draft email, run your eye over every clause starting with who / which / that. For each one, ask yourself: do I mean which one, or am I just adding a side fact? That six-second check catches most errors before you hit Send.

Quick recap: - Defining clauses filter the set: only these invoices, these candidates, this entrance. - Non-defining clauses add asides about someone or something already clearly identified. - Remove the clause: meaning fails, it's defining; meaning holds, it's non-defining. - Keep the clause tucked right next to its noun to protect sense.

Advanced (Mastery)

Once the two jobs are solid under your feet, mastery becomes about register, density, and choosing the lightest structure that still gets the job done.

Dense embedding. You can nest relative clauses inside one another:

The proposal that the team who rebranded the product prepared is on your desk.

Readable, if each clause sits hard against its own noun. Go two or three layers deep and most workplace readers will silently start wishing you'd written two sentences instead. Clarity beats cleverness, every time.

Style signals around that and which. In careful British professional writing you'll see both that and which in defining clauses; that is less welcome once you're in non-defining territory. American editorial culture is stricter still — that means defining, which (with commas) means non-defining, full stop. For a British workplace email, either choice is generally fine as long as the job of the clause is right; for international reports, mirroring the US preference on that/which can quietly silence some style-sheet complaints. The full pronoun picture, again, is Pillar 2's to teach.

Relative clause vs. appositive. Same "extra info" intention, different tools entirely:

• Relative: Claire Davies, who is our interim CFO, will join at 3.
• Appositive: Claire Davies, our interim CFO, will join at 3.

The appositive is lighter — no relative pronoun, no finite verb doing extra work. When the extra information is really just a title or a short rename, reach for the appositive instead. The full contrast and guidance on when to choose each lives at article 6.3.

Reduced relatives — a forward look. You'll meet things like the candidate applying for the senior role instead of the candidate who is applying for the senior role. Those are reduced relative clauses (article 3.5). They're almost always compressed defining clauses, and they're genuinely useful in CVs and executive summaries once you're confident the who's doing what is still obvious to the reader.

Register, and when not to hang a clause at all. Non-defining relatives can make writing sound polished and considered. Overuse them and you get bureaucratic sludge instead:

Padded: Our partners, who are based in five countries, which includes markets in Asia that we entered last year, have requested a call.

Cleaner: Our partners, based in five countries including Asian markets we entered last year, have requested a call. (Or, better still, two sentences.)

Mastery here is knowing the difference between a detail worth embedding and one that should simply breathe as its own sentence. And here's an honest aside from years of editing client reports: half the "wrong" relative clauses I flag aren't wrong by rule at all — they're just attached to the wrong noun. Re-read and ask, always: what is this clause actually describing?

Common Mistake: Treating a long, worthy fact as a non-defining relative when a fresh sentence would serve your reader far better. Heavy: The supplier, which has factories in the Midlands and which recently passed our audit after three failed attempts last year, has cut lead times. Better: The supplier, which has factories in the Midlands, has cut lead times. It recently passed our audit after three failed attempts last year. Advanced writers know when embedding stops helping and starts burying the point.

Pro-Tip: On a knotty paragraph, read the bare main clause alone first — spine only. If that spine holds up on its own, then decide what genuinely belongs inside as a defining filter, and what can either ride along as non-defining colour or simply become its own sentence.

Quick recap: - Nest relative clauses only when each one sits tight against its own noun. - Prefer light structures — appositives, reduced forms — when they carry the meaning just as well. - That/which preferences differ slightly UK/US; the job the clause is doing matters far more than the brand war. - Use non-defining relatives for genuine colour, never as padding.

UK vs US Usage

The functional split itself is shared ground: defining (restrictive) vs. non-defining (non-restrictive). The labels differ more than the logic underneath them. UK materials favour defining/non-defining; US materials favour restrictive/non-restrictive.

The real, practical divergence is almost entirely about relative pronouns and style-sheet habit: US editors push that for restrictive clauses and which for non-restrictive ones, commas and all. British English more readily lets which do both jobs. Comma craft around non-defining clauses is genuinely common ground between the two varieties, and it's covered in full in the Punctuation pillar — not here. Pronoun morphology and case (who/whom) stay with Pillar 2, where they belong.

Writing for a UK audience, use defining/non-defining with confidence. Writing for a US-trained reader, borrow their restrictive/non-restrictive labels — and don't invent bigger differences than genuinely exist. There aren't many, and manufacturing them helps nobody.

Key Takeaways

• Relative clauses modify nouns; defining ones select, non-defining ones add.
• Defining = restrictive; non-defining = non-restrictive — same jobs, different name badges.
• Remove the clause: broken or vague means defining; still clear means non-defining.
• Keep the clause next to its noun — misplaced ones create real, sometimes expensive, confusion.
• Pronouns are Pillar 2's job; comma rules for non-defining clauses are the Punctuation pillar's job.
• Prefer the lightest structure that still does the work — appositive, reduced relative, or simply a clean new sentence.

Check Your Understanding

1. Defining or non-defining? Applicants who miss the deadline will not be considered.

2. You're describing your only line manager, and the length of service is extra. Which is right? a) My manager who started in 2019 is retiring. b) My manager, who started in 2019, is retiring.

3. Why is the following not a complete sentence on its own? Which we discussed in Tuesday's stand-up.

4. True or false: a non-defining relative clause and an appositive can both supply extra information about a named person; the appositive just does it with no relative pronoun and no finite verb of its own.

5. Apply the remove-it test. Defining or non-defining? Laptops that have encrypted hard drives may leave the building.

Answer key

1. Defining — only those applicants who miss the deadline are excluded.
2. (b) — one manager already identified; "who started in 2019" is non-defining (comma detail lives in the Punctuation pillar).
3. It's a dependent clause — no complete thought without a main clause to attach to (see 3.1).
4. True — same communicative job, different structure (see 6.3 for the full contrast).
5. Defining — remove it and "Laptops may leave the building" loses the essential filter entirely.

Internal Links

• Back to: Pillar 2 — Relative Pronouns (forms and choice of who / which / that / whose).
• Routing: 3.0 Clause map.
• Also in Pillar 3: 3.1 Independent vs. Dependent Clauses · 3.5 Reduced Clauses.
• Contrast: 6.3 Appositives (non-defining relatives vs. noun-phrase renames).
• Watch out for: 5.3 Misplaced Modifiers (when a relative clause detaches from its noun).
• Forward to: Punctuation pillar (comma rules for non-defining/non-restrictive clauses).