Apostrophes are used in contractions to replace letters that have been omitted for brevity. cannot becomes can't, do not becomes don't.


Apostrophes are used to show possession. That cat's meow. The button's hole cards. Stella's groove. One notable exception is the word its. "Its" is ALWAYS possessive, "it's" ALWAYS means it is.


When an s has been added to a word to make it plural the apostrophe follows the "s" to show a possessive plural such as the girls' locker room. Of course it could be the girl's locker room but then it is a locker room for only one girl.


An interesting misuse of an apostrophe shows up in print all the time. How many cards have four spots? There are four 4's in a deck. The apostrophe here is wrong and it should be 4s.