Whose vs. Who's: What's the Difference?
Quick Answer
whose = possessive pronoun (belonging to whom)
who's = contraction of "who is" or "who has"
Explanation
WHOSE (possessive)
Asks about or shows ownership
Like: his, her, their, its
"Whose jacket is this?"
"The student whose essay won."
"A city whose history is rich."
WHO'S (contraction)
Short for "who is" or "who has"
who's = who is / who has
"Who's at the door?" (who is)
"Who's been using my computer?" (who has)
Quick test: Replace with "who is" or "who has". If it still makes sense → use who's. If not → use whose.
Examples
Common Mistakes
Incorrect: I don't know who's book this is.
Correct: I don't know whose book this is. (Test: "who is book" ✘ → use whose)
Incorrect: Whose responsible for this mistake?
Correct: Who's responsible for this mistake? (Test: "who is responsible" ✔ → use who's)
Practice
Fill in the blank:
"_____ the new manager? And _____ office is that?"