The term energy unit refers to a unit of measurement used to quantify the amount of energy in a system. The most commonly used energy units are the ERG (3 letters), rad (3 letters), kilowatt (8 letters), JOULE (5 letters), and dyne (4 letters). An ERG is a unit of energy equal to 10−7 joules, a rad is a unit of absorbed radiation dose equal to 0.01 joules per kilogram, a kilowatt is a unit of power equal to 1000 watts, a JOULE is a unit of energy equal to one watt-second, and a dyne is a unit of force equal to 10 newtons.