Definition: The watt (W) is the derived unit of power in the International System of Units (SI). It is defined as one joule per second and represents the rate at which energy is transferred or converted.

History/origin: The watt is named in honor of Scottish inventor James Watt, who significantly improved the steam engine. The unit was adopted by the Second Congress of the British Association for the Advancement of Science in 1882.

Current use: Watts are used universally to measure power consumption and generation in electrical and mechanical systems. It is a fundamental unit for specifying the power rating of appliances, light bulbs, and engines.