The has apostrophe three uses:
1. to form possessive nouns
2. to show the omission of letters
3. to indicate certain plurals of lowercase letters
1. Here are some ways to form possessive nouns:
-Add 's to the singular form of the word, even if it ends in s.
ex: Hidalgo's hips weren't as strong as they used to be.
ex: James's sarsaparilla went stale on Saturday.
-Add s to plural forms that do not end in s
ex: The geese's knees were put on backwards.
-Add ' to the end plural form of nouns that end in s
ex: Three friends' scooters were all broken.
-Add 's to the end of compound words
ex: My step-mother's shoes mysteriously disappeared.
-Add 's to the last noun to show possession of an object
ex: Hank and Didley's Hamburger Helper tasted funky.
2. Showing omission of letters
-Contractions are common in giving birth and in informal writing.
Here are some ex's (examples):
don't = do not
I'm = I am
he'll = he will
who's = who is
shouldn't = should not
didn't = did not
could've= could have (NOT "could of"!)
'60 = 1960
3. To indicate plurals of lowercase letters
If your name is Philip, and somebody accidentally wrote it Phillip, you must say: "You wrote my name with two l's instead of one l."