Dealer Definition. A Dealer is an individual or firm that acts as a principal or counterparty to a stock, commodity or currency transaction. Principals take one side of a position, hoping to earn a spread by closing out the position in a subsequent trade with another party. In contrast, a broker is an individual or firm that acts as an intermediary, putting together buyers and sellers for a fee or commission. A Dealer in forex is any type of financial institution that has received authorization from a relevant regulatory body to act as a dealer involved with the trading of foreign currencies. Dealing with authorized forex dealers ensure that your transactions are being executed in a legal and just way. In the United States, one regulatory body responsible for authorizing forex dealers is the National Futures Association (NFA). The NFA ensures that authorized forex dealers are subject to stringent screening upon registration and strong enforcement of regulations upon approval. The NFA is a subsidiary of the Commodity Futures Trading Commission (CFTC).