What is the correct spelling of possessive nouns ending in s?

Answer 1

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: class'

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

Examples:

The class' assignment is due on Monday.

The class's assignment is due on Monday.

For plural nouns that end with an s, an apostrophe (') is added to the ending s.

Example: The classes' assembly is scheduled for ten.

Answer 2

For singular possessive nouns ending in s, add an apostrophe followed by another s, such as "Thomas's book." For plural possessive nouns that end in s, just add an apostrophe after the s, like "the cats' toys."