Possessive Case of Nouns

Possessive nouns show ownership of something by someone or something specific by adding ‘s to the end of a singular noun or an apostrophe to a plural noun.

For example:

the girl‘s books

the girls’ books

In singular nouns of more than one syllable that end in an s-sound, only the apostrophe may be added. For plural nouns that do not end in s, add only the apostrophe.