I can't stand it anymore. To everybody, everywhere:
Apostrophes do 1 of 2 things:
1. Denote possession
2. Denote contraction
Here's how you use them:
- If you possess it, and you don't have an S on your name, easy: [Pepper's broccoli].
- If you possess it, and you have an S on your name, easy: [The Jones' broccoli].
- TIP: [The Jones's brocolli] would be awkward. DBA [don't be awkward]. It's a plural possessive and should be [The Joneses' broccoli]. Except the Joneses hate broccoli.
- Yours, His, Hers: already possessive. No apostrophe. Ever.
- Can + Not = "Cannot"; becomes [Can't]. The apostrophe symbolizes the contraction and disappearance of two letters.
- "Is not" becomes [isn't]. The apostrophe symbolizes the contraction and disappearance of one letter.
- [Its] is possessive but has no apostrophe. Why? Because:
- [It's] was already taken, and is short for "It is".
- Correct: It's difficult to use apostrophes.
- Correct: Grammar--its importance should not be overlooked.
- Beaver's build dams.
- Beavers' build dams.
- If it ends in X or Z. But let's not open that can of worms.
An addendum for Pete:
You + Are = You're
Your = possessive.
Example: You're loose unless you tighten your grammar.