10 Grammar Rules Every Teacher Should Know

You’re a mean one, Mr. Grinch. (You are a mean one)
Your heart is made of coal. (the heart belonging to you)

• 
  “Whose” means “belonging to the person mentioned before” as in:
  

The Grinch, whose heart was made of steel, stole Christmas. (the heart of the Grinch)

• 
  “Who’s” is a contraction for “who is” as in:
  

Who’s that masked man? (who is he?)


Short Cut
Like “it’s” “you’re” and “who’s” can be replaced with the full form, “you are” and “who is,” respectively. If the full form doesn’t make sense in the sentence, the correct spelling is “your” or “whose.” And—you probably guessed this was coming—“your” answers the question “whose is it?” and “whose” is the very question that proves possession in the first place.