who

What person or people; which person or people; asks for the identity of someone; used in a direct or indirect question.

• You're getting married‽ Who to? (direct question)
• I don't know who it is. (indirect question)
• Who says they care? —They themselves do.

Introduces a relative clause having a human antecedent. With antecedent as subject.

• That's the man who works at the newsagent. (defining)
• My sister, who works in the accounts department, just got promoted to manager. (non-defining)
• That's the man who I saw earlier.

With antecedent as subject.

• That's the man who works at the newsagent. (defining)
• My sister, who works in the accounts department, just got promoted to manager. (non-defining)

With antecedent as object: whom.

• That's the man who I saw earlier.
• My brother, who you met the other day, is coming to stay for the weekend.

Whoever, he who, they who.

• Who dares wins.
• Who insults my mother insults me.
• Give it to who deserves it.

Also used with names of collective nouns that are groups of people, especially singularly-named musical groups or sports teams.

• Who are the Miami Heat?

A person under discussion; a question of which person.

whose

• Who phone just rang?