Incorrect apostrophe usage is one of my personal pet peeves. It’s very tempting to add an apostrophe before every “s” that ends a word—but that’s the most amateur mistake you can make!
Fortunately using apostrophes correctly is actually really easy. There’s just a few simple rules you have to remember.
Using apostrophes for possession
Use an apostrophe and an “s” when you’re indicating that something belongs to someone:
Correct: That was Gollum’s ring! Why did Bilbo have to steal it?
When the thing doing the possessing already ends with an “s”, then put the apostrophe after the existing “s”:
Correct: Legolas’ bow got a good workout in Lord of the Rings.
Correct: Frodo soon grew tired of the elves’ lembas bread.
But don’t add an apostrophe for possessive pronouns:
Incorrect: Bilbo was his name, and Sting was his’ sword.
Correct: Bilbo was his name, and Sting was his sword.
Incorrect: The Eye of Sauron swept it’s gaze all across Mordor.
Correct: The Eye of Sauron swept its gaze all across Mordor.
Using apostrophes to indicate missing letters or contractions
Use an apostrophe when you’re shortening or combining words.
you are becomes you’re
do not becomes don’t
it is or it has becomes it’s (Note that this is one of the most common mistakes of the amateur writer. Don’t mistake it’s and its!)
he is becomes he’s
in and out can optionally become in ‘n’ out (because you’re removing both the leading “a” and the trailing “d” in “and”.)
Common apostrophe mistakes to avoid
If an agent or publisher spots one of these mistakes, it’s straight to the slush pile with you—after all, if a writer doesn’t understand fundamental grammar, then the copyediting for their work will cost more than it’ll earn!
Using you’re instead of your, and vice versa. You’re is short for you are. Your indicates that you are possessing something.
Using it’s instead of its, and vice versa. It’s is always short for it is or it has. Its indicates possession, and you don’t use an apostrophe.
Forming plurals with apostrophes.
Incorrect: All the hobbit’s in the fellowship loved second breakfast. (The hobbits are not possessing anything; plurals don’t use apostrophes.)
Correct: All the hobbits in the fellowship loved second breakfast.
Incorrect: I ordered fifteen Lord of the Rings DVD’s when they came out. (The DVDs are not possessing anything either.)
Correct: I ordered fifteen Lord of the Rings DVDs when they came out.
There are a few rare exceptions that you can look up on a case-by-case basis, but by and large these few rules are really all there is to it. Do you want to indicate that one thing belongs to another, or that you’re removing words or letters from a phrase? Then there’s going to be an apostrophe in there somewhere. Otherwise, or when in doubt, don’t use an apostrophe!