Possessive Pronouns vs Determiners

You hand in a piece of homework you're rather pleased with, and it comes back with a small red circle around one word: "That pencil case is my." No explanation, just check this in the margin. Or you text a friend — "Whose coming to the park later?" — and they reply, unhelpfully, "who's, you numpty." Or you freeze on your own sentence: the dog wagged its tail. Its? It's?

None of this is because you're not clever enough, or weren't paying attention in Year 7. It's because a handful of very short, very similar-looking words are quietly doing two completely different jobs — and almost nobody ever sits you down and shows you which job is which. That's what we're doing here: sorting mine from my, then using exactly the same thinking to crack the big traps that catch out even strong writers: its/it's, whose/who's, your/you're and their/there/they're.

The two families

Possessive determiners sit in front of a noun and tell you who owns the thing that comes next:

my pencil, your homework, his jacket, her phone, its lid, our classroom, their teacher

Possessive pronouns stand alone — no noun needed, because it's already clear what's being talked about: mine, yours, his, hers, ours, theirs.

• "That pencil case is mine." (= my pencil case)
• "Is that bag yours?" (= your bag)
• "The red hoodie is hers." (= her hoodie)

Same ownership, two different jobs: the determiner sits glued to a noun; the pronoun has already swallowed the noun and stands there quite happily on its own. Here's the test, and it works almost every time: does the word need a noun stuck to it, or can it finish the sentence by itself?

• "This is my ___" — needs a noun. My what? → determiner.
• "This is mine." — complete. Nothing missing. → pronoun.

Try it the wrong way round and you'll hear it instantly: "This pencil case is my." ❌ (My what?) "This is mine pencil case." ❌ (You've glued a pronoun to a noun.)

One oddity: its is the odd one out. Every other word has a matching stand-alone pronoun — her/hers, our/ours, their/theirs — but its doesn't. You'd never say "That collar is its." If you need ownership to stand alone for something called it, you rephrase ("That's its collar"), or name the owner: "That's the dog's."

The big traps: possession vs contraction

Now the words that actually cause the trouble in your exercise books: its/it's, whose/who's, your/you're and their/there/they're. These aren't really about pronouns versus determiners any more. They're about possession versus contraction — a contraction being two words squashed into one, with an apostrophe standing in for the letters that got dropped. That gives you one test, used four times over: expand the word and see if it still makes sense.

its vs it's — its (no apostrophe) shows possession, exactly like my, your, her; it's is short for it is or it has.

• "The dog wagged it's tail." → "the dog wagged it is tail." Nonsense → its.
• "I think it's going to snow." → "I think it is going to snow." Works → it's.

whose vs who's — whose shows possession; who's is short for who is or who has.

• "Do you know whose phone this is?" → "who is phone this is"? Nonsense → whose.
• "Who's finished their homework?" → "Who has finished"? Fine → who's.

your vs you're — your = possession ("Is that your coat?"); you're = you are. Test: "You're late" → "You are late." ✓

their vs there vs they're — their = possession; there = a place, or "there is/are"; they're = they are. Ask three quick questions in order: a place? → there. Saying "they are"? → they're. Something belongs to them? → their.

The apostrophe in these little words never means ownership — it means letters are missing.

Watch out: the finer corners

• After "of," use the pronoun. It's "a friend of mine," never "of my" — there's no noun after "of" for a determiner to attach to.
• Determiners can't double up. "the my keys" ❌, "a her jacket" ❌ — you can't stack a determiner in front of another determiner.
• His does both jobs. "That's his jacket" (determiner) and "The jacket is his" (pronoun) — same spelling, two roles.
• No apostrophe, ever. No possessive pronoun or determiner takes one — its, hers, ours, theirs, yours are all apostrophe-free. History split the jobs: 's on a noun shows possession (the cat's whiskers); 's on a pronoun shows a missing letter (it's, who's, you're).
• Whose works for things too. "A book whose ending surprised everyone" is entirely standard — not just for people, and it has been for centuries.

Quick check

1. Choose: a) "Is this (your / you're) pen?" b) "I think (its / it's) going to be sunny." c) "That blue bike is (her / hers)." d) "Do you know (whose / who's) won the match?" e) "The team lost (its / it's) captain to injury."

2. Fix: "The dog chased it's tail until it was dizzy."

3. Pronoun or determiner? a) "That folder is mine." b) "I can't find my folder." c) "The car is theirs."

4. Fill with their / there / they're: a) "I think ___ going to win the tournament." b) "Put your shoes over ___."

5. "Who's book is this?" or "Whose book is this?"

UK vs US Note

This is one of the tidier corners of grammar — possessive pronouns and determiners work identically in UK and US English: mine/my, yours/your, its/it's, whose/who's, with no spelling differences and no rule differences on either side of the Atlantic. The only thing that changes is terminology: what I've called a full stop here, an American teacher would call a period [US: period]. Otherwise, everything in this article applies exactly the same way whichever English you're learning.

Where next

• Personal Pronouns — the wider system these possessives belong to
• Verbs and Contractions — for how words like it's, who's, you're, they're get squashed together in the first place
• Possessive Nouns and Apostrophes — for the dog's bone, the girls' toilets — a different system from the one covered here, worth reading alongside it
• Determiners — for the full inventory of determiners and how my/your/its slot into a noun phrase