1. The possessive form of who.
2. The possessive form of which.
[Middle English whos, from Old English hwæs; see kwo- in Indo-European roots.]
Usage Note: It has sometimes been claimed that whose is properly used only as the possessive form of who and thus should be restricted to animate antecedents, as in a man whose power has greatly eroded. But there is extensive literary precedent for the use of whose with inanimate antecedents, as in The play, whose style is rigidly formal, is typical of the period. In an earlier survey this example was acceptable to a large majority of the Usage Panel. Those who avoid this usage employ of which: The play, the style of which is rigidly formal, is typical of the period. But as this example demonstrates, substituting of which may produce a stilted sentence. See Usage Notes at else, which, who.
of or relating to whom or which especially as possessor or possessors
agent or agents , or object or objects of an action
a. of whom? belonging to whom? used in direct and indirect questions I told him whose fault it was whose car is this?
b. (as pronoun) whose is that?
2. of whom; belonging to whom; of which; belonging to which: used as a relative pronoun a house whose windows are broken
[Old English hwæs, genitive of hwā who and hwæt what]
Collins English Dictionary – Complete and Unabridged © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003
Whose means "belonging to the person":
e.g. "Dan, whose eyes were bloodshot, hadn't slept well."
Whose is a possessive pronoun.
e.g. whose cat, whose iPod, etc.