The possessive ‘s, or genitive case, shows that something belongs to someone, as in Mary’s book. Add ‘s to singular nouns and names, add only an apostrophe to plural nouns ending in s, and add ‘s to irregular plurals like children.
Grammar Rule
The apostrophe always marks who owns the thing.
Possessive ‘s: Rules and Examples
| Case | Rule | Example |
|---|---|---|
| Singular / name | add ‘s | Mary’s book is red. Tom’s phone is here. |
| Plural ending in s | add only ‘ | My parents’ house is big. |
| Irregular plural | add ‘s | The children’s toys are new. |
Remember: the apostrophe always marks who owns the thing.
Practice Test
Instructions
Answer each question in the test below using the correct possessive form. You will get a new random set of questions every time you retake the test, plus a downloadable results summary with your name and score at the end.
Possessive 's (Genitive case)
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Frequently Asked Questions
What does the possessive ‘s show?
The possessive ‘s shows that something belongs to someone, as in Mary’s book.
How do you form the possessive for a plural noun ending in s?
Add only an apostrophe after the s, as in my parents’ house.
How do you form the possessive for an irregular plural like children?
Add ‘s, as in the children’s toys.
Does the possessive ‘s change for singular names?
No. Singular names always add ‘s, as in Tom’s phone or Mary’s book.