The ' mark is called an apostrophe. It has four uses:.
1. The apostrophe indicates possessive forms of nouns..
"Mary's book, " "The dog's bed".
2. The apostr…ophe indicates the omission of letters:.
will not = won't.
do not = don't.
I am = I'm.
3. The apostrophe indicates pluralized nouns (note: there is some question as to the necessity of this usage):.
"How many no's were counted on the ballot?".
4. The apostrophe is used in some last names..
O'Brien, O'Donnell, D'Arby, etc. (MORE)