4.14 describe power as the rate of transfer of energy or the rate of doing work

Power is the rate of energy transfer, or the rate of doing work, it is different to force and energy. The unit for power is watts (W), 1 watt = 1 joule of energy transferred per second. This means a watt is the same as a 'joule per second', they are interchangeable, watt is more commonly used just because few people may get confused with 'joule' and 'joule per second' (which are vert different things).