business firm vs concern

business firm and concern both are nouns.

Word	Noun	Adjective	Verb	Adverb
business firm	Yes	No	No	No
concern	Yes	No	Yes	No

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

business firm: the members of a business organization that owns or operates one or more establishments
concern: a commercial or industrial enterprise and the people who constitute it

Other hypernyms of business firm include business, business concern, business organisation, business organization.

business firm (noun)	concern (noun)
the members of a business organization that owns or operates one or more establishments	something that interests you because it is important or affects you
	something or someone that causes anxiety; a source of unhappiness
	a feeling of sympathy for someone or something
	an anxious feeling
	a commercial or industrial enterprise and the people who constitute it

business firm (verb)	concern (verb)
	be relevant to
	be on the mind of