A possessive is a word that shows possession or ownership of something. A possessive can be a noun, pronoun or adjective. Nouns are usually made possessive by adding an apostrophe and an ‘s’.

A singular noun is a noun referring to just one person or thing, for example 'cat'. When you want to show that something belongs to that person or thing, you add a possessive apostrophe and an 's'.

On October 22nd, at 2:50 P.M., @APStylebook tweeted a series of guidelines about how to punctuate possessives of nouns that end in “S”: “For possessives of plural nouns ending in s ...