Nouns have a possessive form which is used to show ownership. Such nouns are called possessive nouns. They show ownership by adding an apostrophe and an s ( 's ) or just an apostrophe to a noun.
Apostrophe (') and an s ('s) after singular noun to show possessive form
Place an apostrophe and an s after a singular noun to show it is the owner of the noun that follows.
Apostrophe (') and an s ('s) after plural noun to show possessive form
If a noun is plural and does not end in an s, add an apostrophe and an s to the end of the plural noun.
Only apostrophe is added to plural noun
If a noun is plural and ends in an s, add only an apostrophe to the end of the plural noun. No s need follow the apostrophe.
Apostrophe or no apostrophe after noun ends in s
When a proper noun ends in s, the possessive form can take either an apostrophe and an s or only an apostrophe.
Possessive noun not followed by noun
So far, all possessive nouns are followed by nouns as shown above. But if a noun (for example, a place of business) is understood, a possessive noun with its apostrophe and s is not followed by the noun.
Two possessive nouns one after the other
Sometimes two possessive nouns appearing one after the other may be necessary to indicate double ownership.
Apostrophe indicates joint ownership
When two nouns are joint owners of another that follows, only the second noun is in the possessive form of an apostrophe and an s.
Apostrophes indicate different owners
When two nouns are owners of different assets, each of the two possessive nouns needs an apostrophe and an s.
Compound possessive nouns
If it is a hyphenated compound noun, add the apostrophe s ( ‘s ) to the last word.