Possessive nouns show ownership or possession and are formed by adding an apostrophe and sometimes an "s" to a noun. They modify another noun to indicate something is possessed or owned. The possessive form is used as an adjective. Examples of correct possessive nouns include John's book, Kerry's car, and Grandma's mirror. When a plural noun ends in "s", only an apostrophe is added. Understanding possessive nouns is made easier through examples that demonstrate how to form them and what they indicate about ownership.