A possessive noun shows ownership. Possessive nouns are formed by adding an apostrophe and "s" or only an apostrophe.

See the words that tell who owns the bicycles?

1. One girl's bicycle was pink.
2. The twins' bicycle has two seats.
3. The men's bicycles have large frames.

The words "girl's", "twins' ", and "men's" are possessive nouns. The possessive form of a noun shows that the person or thing named owns something.