When to use s' or 's after words ending with an s?

Answer 1

Possessive form for nouns ending in 's':

For singular nouns ending with 's' (class, Mr. Jones) both forms are accepted, class' or class's, Mr. Jones' or Mr. Jones's,

For plural nouns ending with 's' (classes, the Joneses) an apostrophe is added to the end of the word, classes', the Joneses'.

I'll just give you some examples:

's is almost always used: chair's (one chair), man's, men's, Tom's, Jess's, Jesus's, Moses's, Socrates's

s' shows OWNERSHIP to PLURAL NOUNS ENDING IN "S" ONLY. NEVER to names ending in "s," as names are NOT plural. You have to be able to answer "yes" to both questions:

1) Is it more than one person, place or thing? (not just one boy, but boys...not just one chair, but chairs) 2) Does the plural noun end in "s"? ("Men" does not qualify - it is plural, but without an "s" on the end. "Children" does not qualify either. "Boys" and "chairs" both qualify.)

ex. the chairs' legs (legs from many chairs), boys' (belonging to multiple boys) ex. The boys' lockers smelled like old socks.

Answer 2

Use 's with singular nouns ending in s to show possession (e.g., the boss's office). Use s' with plural nouns ending in s to show possession (e.g., the students' textbooks).