steam bath vs bathing

steam bath and bathing both are nouns.

Word	Noun	Adjective	Verb	Adverb
steam bath	Yes	No	No	No
bathing	Yes	No	No	No

As nouns, bathing is a hypernym of steam bath; that is, bathing is a word with a broader meaning than steam bath:

steam bath: you sweat in a steam room before getting a rubdown and cold shower
bathing: the act of washing yourself (or another person)

Other hypernyms of steam bath include washup.

steam bath (noun)	bathing (noun)
you sweat in a steam room before getting a rubdown and cold shower	immersing the body in water or sunshine
a room that can be filled with steam in which people bathe; `vapour bath' is a British term	the act of washing yourself (or another person)