Grammar 101: Who's vs. Whose
This Grammar 101 is a good one: it’s easy to learn and almost guaranteed to be on every ACT and SAT!
The long answer is that “who’s” i s a contraction, short for “who is” or “who has.” Even though it has an apostrophe, “who’s” DOES NOT indicate possession. On the other hand, even though it does not have an apostrophe, “whose” is a pronoun that does in fact indicate possession.
If your eyes glazed over a bit when you read any or all of the words pronoun, apostrophe, or contraction, here’s the short answer. Every time you’re trying to decide between “who’s” and “whose,” put the phrase “who is” into the sentence and let your ears do the work. If “who is” sounds good in the sentence, then use “who’s.” If “who is” sounds awkward, use “whose”.
For example, look at this sentence: Who’s/whose book is this?
Insert “who is” into the sentence and see how it sounds: Who is book is this?
That sounds awful, so “who is” can’t be the right word for the sentence. Use “whose” instead: Whose book is this?
One more example: Who’s/whose the best basketball player of all time.
Again, insert “who is” into the sentence and see how it sounds: Who is the greatest basketball player of all time?
That doesn’t sound awkward at all, so “who’s” is the right word this time: Who’s the greatest basketball player of all time?
That’s it! Short and sweet.