Center for Writers - Resources
APOSTROPHES

 The apostrophe (') can be used in a number of ways:

1.  To show possession in nouns, indefinite pronouns and adjectives

           Examples: the boy's dog (singular noun), the boys' dogs (plural noun), the children's coats
           (irregular plural noun), no one's fault (singular indefinite pronoun), a day's pay (singular
          sense adjective), three months' maternity leave (plural sense adjective)

2. To show the omission of letters in contractions

        Examples: doesn't (does not), haven't (have not), hasn't (has not), don't (do not),
           I'd (I would), she's (she is), it's (it is)

3. To form the plurals of numbers and letters

          Examples: 10's, 100's, the 1970's, mind your p's and q's, write your a's and b's

4. To show the omission of numbers, especially in writing years

          Examples: the class of '73, the team of '72, sweet '45