A security or contract whose value is dependent on or derived from the value of some underlying asset. The main classes of derivative instruments are: forwards, futures, options (and their securitized equivalents, warrants) and swaps. There are derivative contracts on currencies, commodities, equities, interest rates, credit or default events, indices and baskets in all these asset classes and combinations of all of them. Derivatives can be exchange-traded or traded over-the-counter (OTC). The latter are contracts between counterparties and are telephone and screen traded by banks outside the regulated exchanges.