What's the difference between "infirmary" and "sick-bay"?
Are they completely synonymous?
An infirmary is a kind of facility on its own, though it could be part of a larger institution such as a large hospital or medical complex.
A sick bay has originally been a part of a ship or military camp/ military base, but may now be any part of a larger medical facility.
The difference thus being that an infirmary is essentially a standalone unit while a sick bay is more of a portion set aside for the purpose.
The terms may be used interchangeably in actual practice, though.
n. a hospital or dispensary, esp. aboard ship.
(ĭn-fûr′mə-rē) n. pl. in·fir·ma·ries
A place for the care of the infirm, sick, or injured, especially a small hospital or dispensary in an institution.
According to this link, there is a difference between the American and British definitions of infirmary http://dictionary.cambridge.org/dictionary/british/infirmary?q=infirmary
A sickbay is a room with beds for people who are ill, especially on a ship http://dictionary.cambridge.org/dictionary/british/sickbay?q=sickbay
Infirmary is a building used as a hospital, or a large area used as a hospital, whereas sick-bay usually refers to a smaller area such as a room meant for the purpose.