"A third party is an entity that is involved in some way in an interaction that is primarily between two other entities. The third party may or may not be officially a part of the transaction between the two primary entities and may or may not be interacting transparently and/or legally. A third party is a party that is involved in, say, a contract or a trade, but is not the main party. A broker to a trade between two counterparties is a third party. In a securities transaction, a law firm, a stock exchange, custody agent, central securities depository, clearing house, calculation agent, paying agent, trustee, a broker-deal etc could be considered third parties that make transactions happen but which are not the principal parties: the issuer and the investor"