sanatorium vs infirmary

sanatorium and infirmary both are nouns.

Word	Noun	Adjective	Verb	Adverb
sanatorium	Yes	No	No	No
infirmary	Yes	No	No	No

As nouns, infirmary is a hypernym of sanatorium; that is, infirmary is a word with a broader meaning than sanatorium:

sanatorium: a hospital for recuperation or for the treatment of chronic diseases
infirmary: a health facility where patients receive treatment

Other hypernyms of sanatorium include hospital.

sanatorium (noun)	infirmary (noun)
a hospital for recuperation or for the treatment of chronic diseases	a health facility where patients receive treatment
pejorative terms for an insane asylum