The possessive case (also sometimes called the genitive case) is the case of nouns and pronouns that denote ownership, possession, or occupancy. For example,
- Susie’s cat ran away.
- I jumped into the driver’s seat.
Having Susie in the possessive case shows that it is her cat that ran away and not someone else’s. It also shows in which seat I jumped. I jumped into the seat that belongs to the driver.
You can form the possessive singular of nouns by adding an apostrophe and an s (‘s). This just means to add an ‘s to all nouns that are singular.
- This is George’s book.
George is only one person, so in order to form the possessive singular we simply add an ‘s.
The possessive plural is formed by adding only an apostrophe (except for a few irregular plurals that do not end in s). For example,
- The Johnsons’ house is very large.
- The puppies’ paws are so cute!
- The children’s books are in the library.
Pronominal possessives (mine, ours, your, yours, his, hers, its, theirs, whose) do not have apostrophes. For example,
- I read a book of hers last year for school.
- Is this yours?
Indefinite pronouns, however, do use apostrophes. For example,
- One must fight for one’s rights.
- I think this is somebody else’s glass.
Multiword compound nouns are formed into the possessive by adding the appropriate ending on the last word. For example,
- My brother-in-law’s music collection is quite impressive.
What about Words Ending in S?
There is some debate whether to include an ‘s after singular words ending in s. For example,
- Dennis’s shoes or Dennis’ shoes?
- Kansas’s schools or Kansas’ schools?
Strunk and White’s famous book The Elements of Style states in rule 1 to add ‘s no matter what the final consonant.
Other Style guides like the Chicago Manual of Style agree largely with Strunk and White, while the AP Stylebook uses only an apostrophe for proper names ending in s and common nouns ending in s where the first letter of the next word is s.
- Dennis’s shoes (correct in Chicago Style)
- Dennis’ shoes (correct in AP Style)
- Kansas’s schools (correct in Chicago Style)
- Kansas’ school (correct in AP Style)
The Chicago Manual of Style does, however, have exceptions to Strunk and White’s general rule and some further options to consider. For more information and style guide specific rules, see our full page on possessives in Chicago Style and AP Style.