As a Noun: 1. A person in the most general sense (without saying who they are exactly). English = someone. 2. A person who does something whose identity does not matter or is not known. English = whoever. 3. A person who has something done to them whose identity does not matter or is not known. English = whomever. As Modifier: 1. Used immediately after a noun sign and before a verb sign to make absolutely clear that the person or thing named in the noun is the actor in the action named in the verb. English = who. 2. Used immediately after a noun sign and before another noun sign followed by a verb sign to mean that the first noun has the action of the verb done to it by the second noun. English = whom. As Question: 1. Used to ask a question about someone's name or the identity of the person who performs the action of the verb in the sentence, or undergoes the action. English = who, whom, which one of you. 2. Used immediately next to a noun to ask questions about the name or identity of the person that the thing belongs to or relates to. English = whose.