Possessive nouns are an essential part of proper English grammar. The possessive form of the noun is simple to learn if you pay attention to a few important rules that most people have trouble with.
Put an apostrophe and an "s" after the word you are making into a possessive, as long as the word does not end with an "s." Then, add the thing that the noun possesses, as in, "The boy's dog."
Place the apostrophe after the final "s" in plural words. For example to speak about papers that belong to a many girls, write "the girls' papers." Do the same if the plural form of a noun ends in "-ies," as in "the babies' blankets."
Use an apostrophe and an "s" in cases where the noun that owns an object ends with an "s." For example, if your boss has a red car, write "my boss's red car." If the word following the noun begins with an "s" then just place the apostrophe without the additional "s," as in "my boss' sports car."
Treat words that are naturally plural such as "women," "children" or "men" as you would treat a regular singular noun by simply adding an apostrophe and then an "s" after the noun and before the object that the noun possesses.
Place the apostrophe and possessive "s" after the second word of a compound noun. For example, if you're talking about the gun that belongs to a police officer, write "the police officer's gun."
Insert an apostrophe after the "s" of a singular word that naturally ends in an "s" such as "mathematics." So, if you wanted to talk about the brightest students of mathematics, write "mathematics' brightest students."
Make a last name plural and then add an apostrophe when talking about something that belongs to a family. It's "the Joneses' home," not "the Jones' home" or "the Jone's home." Of course, you can stop worrying about the apostrophe if you just turn the name into an adjective, instead of a possessive noun; you can say "That brown house is the Jones home."