9. Broker:
A broker is a party that mediates between a buyer and a seller. A broker who also acts as a seller or as a buyer becomes a principal party to the deal.
Distinguish agent: one who acts on behalf of a principal.
A “brokerage” or a “brokerage firm” is a business that acts as a broker. A brokerage firm is a business that specializes in trading stocks.
A sales person working for a securities or commodity brokerage firm is popularly (but incorrectly) called a “broker.” A broker in that context is, strictly speaking, an exchange member who is actually executing the purchase or sales order in the ‘pit’, on the exchange, as a service to the client of the firm for which that salesman works.