1used to ask which person or people a particular thing belongs to: Whose is this? Whose keys are those?2used to show the relationship between a person or thing and something that belongs to that person or thing: That’s the man whose house has burned down. Solar energy is an idea whose time has come.3used to give additional information about a person or thing: Jurors, whose identities will be kept secret, will be paid $40 a day.