men's

possessive case of men: belonging to some or all male humans.

Ellipsis of men’s room (“a lavatory intended for use by men”).

A gents' toilet room might be found in a house that caters for the cheaper class of theatrical patronage, where the slangy language of the "goin' to the mat this aft?" style prevails. A gents toilet room is not found in the Southern Hotel. It either "men's" or "gentlemen's".

Ellipsis of men's department (“an area selling clothing for adult males in a department store”).