Power has many related meanings. We are most concerned with the definition as it applies to physics, where it is known as the measure of the rate at which some work is done. There are a number of different ways and resulting units used to measure power and each has an underlying theme of energy or work. Some examples would be: Horsepower, Joules per unit of time, Foot Pounds of force per unit of time, BTU (British Thermal Units) per unit of time, and watts. Watts are one we frequently encounter in audio as a measure of power partly because watts already have the time component built in to them and provide a convenient reference that’s pertinent to the types of energy transfer we do (moving electricity around). (See WFTD Watt for more background.)