What is the rule of punctuating a possessive noun?

Answer 1

SINGULAR NOUNS

Singular possessive nouns are formed by adding an apostrophe s ('s) to the end of a noun.

Example: I used my grandma's recipe for the cake.

There are two accepted forms for possessive singular nouns ending in s:

Add an apostrophe (') after the existing s at the end of the word: Thomas'

Add an apostrophe s ('s) after the existing s at the end of the word: Thomas's

Examples:

I like Thomas' new bicycle.

I like Thomas's new bicycle.

PLURAL NOUNS

Plural nouns ending in s form the possessive by adding an apostrophe (') after the s at the end of the word.

Plural noun that do not end in s form the possessive by adding an apostrophe s ('s) to the end of the word.

Examples:

The books' covers were damaged in storage.

The children's coats all hung in a row.