The singular form of the plural noun messages is message.
The singular possessive form is message's.
example: The message's content is personal.
The singular possessive form is week's.
The singular possessive form of "classmate" is "classmate's."
The possessive form is Amos's.
The singular possessive form of "gypsy" is "gypsy's."
The singular possessive form of "countries" is "country's".
The singular form is goose; the singular possessive form is goose's.The plural form is geese; the plural possessive form is geese's.
The singular possessive form of county is county's.
Quantum is singular, not singular possessive. The singular possessive form is quantum's.
singular possessive: boy'splural possessive: boys'
The singular possessive form is frontiersman's.
The singular possessive form is aircraft's.
The singular possessive form is contralto's.