infirmary vs hospital

infirmary and hospital both are nouns.

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

As nouns, infirmary and hospital are synonyms defined as:

infirmary and hospital: a health facility where patients receive treatment

infirmary (noun)	hospital (noun)
a health facility where patients receive treatment	a health facility where patients receive treatment
	a medical institution where sick or injured people are given medical or surgical care