The quick answer

Use a possessive adjective — my, your, his, her, its, our, their — right before a noun to show who something belongs to. Say my book, not I book.

The rule

A possessive adjective always comes before a noun and never changes for a singular or a plural noun. The word you choose depends on the owner, not on the thing that is owned: his car and his cars both use his, because the owner (a man) does not change.

Do not confuse a possessive adjective with a subject pronoun. I is the subject of a sentence (I live in Rome); my shows possession (My house is in Rome). The two words never replace each other.

Form

Examples

• This is my phone.
• Is that your jacket?
• Tom is happy with his new bike.
• Anna loves her garden.
• The cat is cleaning its paws.
• We keep our books on this shelf.
• The children left their shoes by the door.

Common mistakes

• ❌ I book is on the table. → ✅ My book is on the table. Use the possessive adjective before a noun, never the subject pronoun.
• ❌ She lost his phone. (about a girl) → ✅ She lost her phone. His and her follow the owner's gender, not the thing owned.
• ❌ The dog wags it's tail. → ✅ The dog wags its tail. Its with no apostrophe shows possession; it's means it is.
• ❌ Their over there with there friends. → ✅ They're over there with their friends. Their shows possession, there is a place, and they're means they are.