The rate at which a light bulb converts electrical energy into light and heat is measured in watts – the electrical energy used per unit of time. Power is the rate with respect to time at which work is done; it is the time derivative of work: where P is power, W is work, and t is time.

Noun. power, authority, jurisdiction, control, command, sway, dominion mean the right to govern or rule or determine. power implies possession of ability to wield force, authority, or influence. the power to mold public opinion authority implies power for a specific purpose within specified limits.