The rules
| Rule | Wrong | Right | Why |
|---|---|---|---|
| One owner: add 's | the girls backpack (one girl) | the girl's backpack | One girl owns it. |
| Plural owner ending in s: add ' | the girl's backpacks (many girls) | the girls' backpacks | The plural is girls; add just an apostrophe to show they own them. |
| Plural not ending in s: add 's | the childrens' toys | the children's toys | The plural is children, so add 's. |
| Plain plurals: no apostrophe | We bought three pizza's. | We bought three pizzas. | Nothing is owned. It is just more than one. |
| Contractions: apostrophe replaces letters | Theyre late. | They're late. | They're = they are. The apostrophe stands where the a was. |
| Possessive pronouns: no apostrophe | The team won it's game. Is this your's? | The team won its game. Is this yours? | His, hers, its, ours, yours, theirs already show ownership. |
Two owners
If two people own one thing together, put the apostrophe on the last name only: Ana and Leo's robot (one robot, built together). If each owns their own, put it on both: Ana's and Leo's phones (two phones).
Worked examples
Example 1: one owner or many?
Problem My three ___ leashes hang by the door. (dog / dogs / dog's / dogs')
- How many dogs? Three. So start with the plural: dogs.
- Do they own something? Yes, the leashes. So show ownership.
- The plural ends in s, so add only an apostrophe.
Answer My three dogs' leashes hang by the door.
Example 2: find the apostrophe mistakes
Problem The Smith's dog lost it's collar, so the kid's next door made poster's.
- The Smith's dog: the dog belongs to the Smith family, a plural owner. The plural is Smiths, so write the Smiths' dog.
- it's collar: the collar belongs to it, so use its. Test: it is collar makes no sense.
- kid's and poster's do not own anything here. They are plain plurals: kids, posters.
Answer The Smiths' dog lost its collar, so the kids next door made posters.
Common mistakes and fixes
| Mistake | Fix |
|---|---|
| Adding 's to make a plural (apple's for sale) | Plurals take no apostrophe: apples for sale. |
| Writing it's for ownership | Say it is. If it sounds wrong, use its. |
| Putting the apostrophe in the wrong place for plural owners | Write the plural first (students), then add the apostrophe (students'). |
| Writing decades with an apostrophe (the 1990's) | Most styles write the 1990s. Use '90s only when letters are left out. |
Practice
Five apostrophe questions
We have three dogs. Which word fits? The ___ leashes were hanging by the door.
- dogs'
- dogs
- dog's
- dogs's
Show answer
Answer: dogs'
There are three dogs, and they own the leashes. The plural dogs ends in s, so add only an apostrophe. Dog's means one dog, dogs shows no ownership, and dogs's is not a standard form.
Which word fits? The ___ toys were all over the floor.
- childrens'
- childs'
- childrens
- children's
Show answer
Answer: children's
Children is already plural and does not end in s, so add 's. Childrens is not a word, and childs' uses the wrong plural.
Which sentence uses apostrophes correctly?
- We bought three pizza's.
- The cat licked it's paw.
- My sister's backpack is blue.
- The Smith's live next door.
Show answer
Answer: My sister's backpack is blue.
One sister owns the backpack, so sister's is right. Pizzas and the Smiths are plain plurals with no ownership, and the cat's paw needs its.
Which word fits? ___ going to be late if we do not leave now.
- They're
- There
- Their
- Theyre
Show answer
Answer: They're
The sentence means They are going to be late, so use the contraction they're. Their shows ownership, there is a place, and theyre is missing its apostrophe.
Ana and Leo built one robot together. Which phrase is correct?
- Ana's and Leo's robot
- Ana and Leo's robot
- Anas and Leos robot
- Ana and Leos' robot
Show answer
Answer: Ana and Leo's robot
For one thing owned together, the apostrophe goes on the second name only. Apostrophes on both names mean each person owns a separate one, which does not match one robot. Anas and Leos drops the apostrophes, and Leos' would mean an owner named Leos.
Frequently asked questions
Is it James' or James's?
Both appear, depending on style. Chicago, MLA and APA add 's (James's). AP style adds only the apostrophe (James'). In school writing that follows MLA or APA, James's is the expected form. Whichever you use, use it every time.
Do you use an apostrophe for plural letters and numbers?
Usually not for numbers: the 1990s, in her 20s. For single lowercase letters, many styles do use one so they are readable: mind your p's and q's. Check your style guide if it matters for an assignment.
Why does its not have an apostrophe if it shows ownership?
Because it is a possessive pronoun, like his and hers, which never take apostrophes. The form it's was already taken by the contraction for it is. If you would not write hi's, do not write it's for ownership.
Sources
- Purdue OWL, Apostrophe Introduction, accessed October 1, 2026
- Purdue OWL, Quotation Marks and Apostrophes, accessed October 1, 2026
