This document discusses possessive nouns and the rules for forming them. There are three main rules: 1) add 's to singular nouns, 2) add only an apostrophe to plural nouns ending in s, and 3) add 's to other plural nouns not ending in s. Possessive nouns show ownership or possession, such as "the woman's coat" to indicate the coat belongs to the woman. Examples are provided to demonstrate the application of each rule.