The quick answer

Use whose to ask who something belongs to, and the possessive 's to answer by naming the owner. Say Whose bag is this? It is Tom's bag., not Who's bag is this? It is Toms bag.

The rule

Whose asks a question about ownership: Whose coat is this? Do not confuse it with who's, a short form of who is or who has: Who's coming? means Who is coming? The two words sound the same but mean different things.

To answer, add 's to a singular name or noun: Tom's bag. For a plural noun that already ends in s, add only an apostrophe: the boys' bikes. For a plural that does not end in s, add 's like a normal name: the children's toys.

Form

Examples

• Whose pen is this?
• This is Tom's pen.
• Who's at the door? (= who is)
• The boys' bikes are red.
• The children's toys are here.
• That is Mrs Green's office.

Common mistakes

• ❌ Toms book is here. → ✅ Tom's book is here. A singular name needs an apostrophe before the s.
• ❌ Who's bag is this? → ✅ Whose bag is this? A question about ownership needs whose, not who's.
• ❌ The childrens toys are here. → ✅ The children's toys are here. Children needs 's like a normal name.
• ❌ The boys's bags are heavy. → ✅ The boys' bags are heavy. A plural that already ends in s only needs an apostrophe, not an extra s.