auction house vs business firm

auction house and business firm both are nouns.

Word	Noun	Adjective	Verb	Adverb
auction house	Yes	No	No	No
business firm	Yes	No	No	No

As nouns, business firm is a hypernym of auction house; that is, business firm is a word with a broader meaning than auction house:

auction house: a firm that conducts auctions
business firm: the members of a business organization that owns or operates one or more establishments

Other hypernyms of auction house include firm, house.

auction house (noun)	business firm (noun)
a firm that conducts auctions	the members of a business organization that owns or operates one or more establishments