An energy derivative which is traded on crude oil (petroleum) and petroleum derivatives (by-products). This includes contracts on crude oil, of which the most widely traded is sweet crudes (Brent and West Texas Intermediate). The underlying may also include heating oil, gasoil, jet fuel, and gasoline. This derivative is also traded on natural gas and gas liquids such as propane (natural gas derivative), in addition to electricity (electricity derivative). All types of standard derivatives (options, futures, swaps, etc) are traded on energy derivatives, including petroleum derivatives. Examples of petroleum derivatives are oil options, oil futures, etc.