A type of trade or instrument which has a value dependent on an observable value, which is usually, but not always, the price of a physical commodity.

The observable value is called the underlier

Detail

Any energy trade type that does not involve immediate delivery is a derivative - because the value of the future delivery varies with the expected price of that commodity at that location at the time of delivery

The only significant exception is a Spot or Prompt trade, which involves immediate, or near immediate delivery