Merriam-Webster Collegiate Dictionary - whose

 I. adjective  Etymology: Middle English whos, genitive of who, what  Date: before 12th century of or relating to whom or which especially as possessor or possessors ~ gorgeous vesture heaps the ground — Robert Browning, agent or agents the law courts, ~ decisions were important — F. L. Mott, or object or objects of an action the first poem ~ publication he ever sanctioned — J. W. Krutch  II. pronoun, singular or plural in construction  Date: 12th century that which belongs to whom — used without a following noun as a pronoun equivalent in meaning to the adjective ~ tell me ~ it was — Shakespeare