Over-the-counter (OTC) is a security traded in some context other than on a formal exchange such as the New York Stock Exchange (NYSE), Toronto Stock Exchange or the NYSE MKT, formerly known as the American Stock Exchange (AMEX). The phrase "over-the-counter" can be used to refer to stocks that trade via a dealer network as opposed to on a centralized exchange. It also refers to debt securities and other financial instruments, such as derivatives, which are traded through a dealer network.