Using the Apostrophe

The apostrophe is used to show ownership and to indicate missing letters in contractions.

I. Apostrophes with Possessive Nouns

    Rule 1:  Add an apostrophe and -s to show possessive case of most singular nouns.
                * the boy's idea        *Mr. Mock's hat        * the policeman's badge

                When  a singular noun ends in -s, you will still add an apostrophe and an -s to show possessive case.
                * James's game        *the boss's anger

                An exception is made when an apostrophe and an -s would make the word difficult to pronounce. 
                Then just add the apostrophe.
                    * I brought Dickens's book along to read. [Awkward]    *I brought Dickens' book along to read. [Better]

    Rule 2:  Add an apostrophe to show the possessive case of most plural nouns already ending in -s or -es.
                    * the sands of the beaches = the beaches' sands        *the strokes of the swimmers = the swimmers' strokes

    Rule 3:  Add an apostrophe and -s to show the possessive case of plural nouns that do not end in -s or es.
                    *the toys of the children = the children's toys        * the hope of the people = the people's hope

II. Apostrophes with Compound Nouns

    Rule 1: Add an apostrophe and -s (or just an apostrophe if the word is a plural ending in -s) to the last word of a compound noun
                Names of Business & Organizations:    *Marks and Morgan's jewelry store        *the Boy Scouts' pledge   
                                                                                *University of Michigan's mascot          *Belk's department store

                Titles of Rulers & Leaders:                    *King Henry VII's reign                        *the Queen of England's children

                Hyphenated Compound Nouns
                Used to Describe People:                    *the Secretary-Treasurer's idea                *her mother-in-law's purse

III. Apostrophes to Show Joint & Individual Ownership

    Rule 1: To show joint ownership, make the final noun possessive.
            *Sara and Bob's books (they share the same books)        *Ron and Mark's apartment (they jointly rent the apartment)

    Rule 2: To show individual ownership, make each noun possessive.
            *Sara's and Bob's books (each one has different books)    *Ron's and Mark's apartments (each has a different apartment)

IV. Apostrophes with Contractions

    Rule 1: Use an apostrophe in a contraction to indicate the position of the missing letter or letters.
            *aren't (are not)        *isn't (is not)            *can't (cannot)                    *shouldn't (should not)       * couldn't (could not)
            * wasn't (was not)    *didn't (did not)        *weren't (were not)             *don't (do not)                    *wouldn't (would not)

            *I'll (I will)                *we'll (we will)         *you'll (you will)                *they'll (they will)             *he'll (he will)
            *who'll (who will)     *she'll (she will)

            *I'm (I am)                  *we're (we are)            *you're (you are)              *they're (they are)               *he's (he is)
            *she's (she is)              *who's (who is)            *it's (it is)                       *Mary's (Mary is)

            *I'd (I would)               *we'd (we would)        *you'd (you would)        *they'd (they would)            *he'd (he would)
            * she'd (she would)      *who'd (who would) 

V. Apostrophes with Pronouns

    Rule 1: Use an apostrophe and an -s with indefinite pronouns to show ownership.
            * another's wish        *nobody's child                *anyone's game            *one's country        *everybody's favorite
            * someone's dog        *one another's choices    *someone else's house

    Rule 2: Do not use an apostrophe with possessive forms of personal pronouns (The following personal pronouns are already
                possessive: my, mine, your, yours, his, her, hers, its, our, ours, their, theirs.)
            *Put your shovel in its bucket.        *His sandcastle is lovely.        * Yours has more colors in it.
            *He wrecked hers.                            * The shovel is ours.                *Its pattern is colorful.