Grammar guide Updated 2026-10-10
Apostrophes and Possessives: Teaching 's, s' and Its
Three rules cover almost every possessive a learner writes: add 's to a singular noun, add only an apostrophe to a plural that already ends in s, and add 's to an irregular plural.
The three core rules
Put these three lines on the board and leave them there for the whole lesson.
| Form | Rule | Example |
|---|---|---|
| singular noun | add 's | the student's book; my sister's coat |
| plural ending in s | add an apostrophe only | the students' books; my sisters' coats |
| irregular plural | add 's | the children's toys; the women's coats; the men's room |
The rule points at the owner, not at the thing owned. A room shared by two boys is the boys' room; a room belonging to one boy is the boy's room. Ask whether the owner is singular or plural, and whether that plural already ends in s.
Names and words that already end in s
Common nouns ending in s behave like any other singular: the boss's office, the bus's door. Names are where the two traditions part company. British style generally writes James's book, while many American publishers write James' book. Both are accepted, so teach consistency rather than correctness. Biblical names are the usual exception, and most guides keep Jesus' and Moses' with the apostrophe alone.
Possessive pronouns take no apostrophe
Six words cause more marking than anything else here: its, yours, theirs, ours, hers and whose. None takes an apostrophe, because each is already possessive. There is no your's, no their's and no its'. The possessive adjectives guide covers the same set from the learner's side.
The confusion comes from two contractions:
- it's means it is or it has: It's cold. The possessive is its: The cat washed its tail.
- who's means who is or who has: Who's coming? The possessive is whose: Whose coat is this?
Test it by saying the sentence aloud with it is in place of it's. If it still makes sense, the apostrophe belongs; if not, the learner needs the plain possessive.
Three other jobs the apostrophe does
An apostrophe marks missing letters in a contraction (don't, I'm, we've) and separates a quotation inside a quotation. It also builds the plural of single letters: mind your p's and q's.
Decades are the disputed case. Most modern guides write the 1990s with no apostrophe and keep 1990's for something belonging to that year. Teach the plain plural as the default; the irregular plurals guide is a useful companion lesson.
Joint or separate ownership
Tom and Anna's house is one house they share, because the apostrophe goes on the second name only. Tom's and Anna's cars means two cars, one each.
Teaching it in three steps
A rules card gives the class something to refer to, an error hunt makes them apply it, and a rewrite task makes them produce it. Ten minutes on the card, then ten and fifteen for the other two. The classroom grammar drills page uses the same shape.
Three classroom drills
Drill 1: apostrophe sorting
Give each pair twenty phrase cards and three labelled trays: singular 's, plural s' and irregular 's. Cards such as the girl's bag, the girls' bags, the children's shoes and my parents' car go into a tray, and the pair has to say why. Add two decoy cards with no possessive at all.
Drill 2: error relay
Write twelve incorrect sentences on the board and send one runner per round to correct a single sentence. Include The student's are late. I like the students book. The dog hurt it's paw. Three book's are missing. Each correction has to be explained to the team before the next runner leaves.
Drill 3: turn it into a possessive
Read a plain sentence and ask for the possessive version. The car belongs to my brother. becomes That is my brother's car. The coats belong to the children. becomes Those are the children's coats. Finish with two owners, The house belongs to Tom and Anna, and let the class argue about the apostrophe before you confirm it.
Errors students make most
- student's are. A possessive apostrophe on a plain plural. It should be The students are late.
- the students book. A missing apostrophe. It should be the students' book for a class, or the student's book for one learner.
- it's tail. A contraction where a possessive is needed. It should be its tail.
- three book's. An apostrophe used to build a plural. It should be three books.
- its'. A possessive pronoun with an apostrophe bolted on. The word is simply its.
- apple's for sale. The same mistake on a shop sign. It should be apples for sale.
How much practice at A2 and B1
At A2, ten short items a day for four days fixes the three core rules. At B1, mix possessives with it's and who's, because the error is then usually a mix-up between the two jobs. A weekly five-minute review, folded into the spelling and word study routine, keeps the rules active.
Frequently asked questions
When do I write 's and when do I write s'?
Add 's to a singular noun, as in the student's book. Add only an apostrophe to a plural that already ends in s, as in the students' books. Irregular plurals that do not end in s take 's, as in the children's books.
Is it James's book or James' book?
Both are accepted. British style usually keeps the extra s, as in James's book, while many American publishers write James' book for names that end in s. Choose one form and keep it consistent through the whole document.
Why is it's wrong in the cat licked it's paw?
Because it's is a contraction of it is or it has, so the sentence would read the cat licked it is paw. The possessive form is its, with no apostrophe: the cat licked its paw.
Do possessive pronouns such as yours and theirs take an apostrophe?
No. Its, yours, theirs, ours, hers and whose are already possessive, so none of them takes an apostrophe. There is no your's, no their's and no its'.
Should I write the 1990s or the 1990's?
Most modern style guides write the 1990s with no apostrophe. The older form the 1990's is still seen, and the apostrophe is kept when the year owns something, as in the 1990's biggest films.