Who’s vs. Whose?
It is extremely easy to be confused with words, especially when they sound the same (i.e., when they’re homonyms). Who’s and whose fall in this category, but each word has a very different meaning and purpose.
Starting with “Who’s,” words with apostrophes are contractions, or words that have been combined. So, “Who’s” is the contracted form of the words “who is” or “who has.”
“Whose,” on the other hand, is the possessive form of “who.”
I’m confused! Who’s (Who is) knocking on whose (possessive form of who = the door belongs to who?) door?
Here’s a trick to remember: if you can replace the word you’re writing with either who is or who has, always use who’s.