fire station vs firehouse

fire station and firehouse both are nouns.

Word	Noun	Adjective	Verb	Adverb
fire station	Yes	No	No	No
firehouse	Yes	No	No	No

As nouns, fire station and firehouse are synonyms defined as:

fire station and firehouse: a station housing fire apparatus and firemen

fire station (noun)	firehouse (noun)
a station housing fire apparatus and firemen	a station housing fire apparatus and firemen