Apostrophes

Apostrophes show possession and indicate omitted letters and numbers.

Apostrophes for Possession
Singular Nouns

Add ’s
    horse’s saddle      knife’s edge      Bob’s cat      book’s cover

Singular Common and Proper Nouns
Add an ’s.
        car’s hood
        David’s hat

Plural Nouns Ending in S
Add an apostrophe only.
    students’ grade

For Irregular Plural Nouns

Add ’s
    Children’s hospital

Do not use an apostrophe for his, hers, yours, theirs, or ours.

Shared vs. Non-shared Possessives
When two or more nouns share possession of the same “thing,” only the last noun takes an apostrophe and s.
       Jack and Jill’s car (the same car is owned by Jack and Jill).
When two or more nouns possess a “thing” independently, each noun gets an apostrophe and s.
       Jack’s and Jill’s car (Jack has a car and Jill has a car—two different cars).

Apostrophes in Contractions
Apostrophes form the contraction of two words—usually indicating missing letters or numbers.
    Do not      Do n(o)t      Don’t
    It is          It (i)s             It’s
    1980s      (19)80s      ’80s

Its vs. It’s
Its is the possessive.
It’s is a contraction of it is or it has.

Use contractions sparingly: avoid in formal writing.