Definitions
1.PronounWhat 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.; Who is coming to your party? Who are your favourite singers?"
2.PronounIntroduces 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.; My brother, who you met the other day, is coming to stay for the weekend."
3.PronounWith 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)"
4.PronounWith 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."
5.PronounWhoever, he who, they who."Who insults my mother insults me.; Give it to who deserves it."
6.PronounAlso used with names of collective nouns that are groups of people, especially singularly-named musical groups or sports teams."Who are the Miami Heat?"
7.NounA person under discussion; a question of which person.
8.Determinerwhose"Who phone just rang?"