Whose v. Who's

USAGE A common written mistake is to confuse who's with whose. The form who's represents a contraction of ‘who is’ or ‘who has’: : who's going to feed the dog?;: I wonder who's left the light on again? The word whose is a possessive pronoun or adjective: : whose is this?;: whose turn is it?


Why hadn't I looked this up before? I wonder how many times I've screwed this up.