brokerage firm vs agent

brokerage firm and agent both are nouns.

Word	Noun	Adjective	Verb	Adverb
brokerage firm	Yes	No	No	No
agent	Yes	No	No	No

brokerage firm (noun)	agent (noun)
a stock broker's business; charges a fee to act as intermediary between buyer and seller	the semantic role of the animate entity that instigates or causes the happening denoted by the verb in the clause
	an active and efficient cause; capable of producing a certain effect
	a businessman who buys or sells for another in exchange for a commission
	a representative who acts on behalf of other persons or organizations
	any agent or representative of a federal agency or bureau
	a substance that exerts some force or effect