The ability or capacity to perform or act effectively. A specific capacity, faculty, or aptitude. Often used in the plural: her powers of concentration. Strength or force exerted or capable of being exerted; might. See Synonyms at strength. The ability or official capacity to exercise control; authority. A person, group, or nation having great influence or control over others: the western powers. The might of a nation, political organization, or similar group. Forcefulness; effectiveness: a novel of unusual power. Chiefly Upper Southern U.S. A large number or amount. See Regional Note at powerful. The energy or motive force by which a physical system or machine is operated: turbines turned by steam power; a sailing ship driven by wind power. The capacity of a system or machine to operate: a vehicle that runs under its own power. Electrical or mechanical energy, especially as used to assist or replace human energy. Electricity supplied to a home, building, or community: a storm that cut off power to the whole region. Physics The rate at which work is done, expressed as the amount of work per unit time and commonly measured in units such as the watt and horsepower. Electricity The product of applied potential difference and current in a direct-current circuit. Electricity The product of the effective values of the voltage and current with the cosine of the phase angle between current and voltage in an alternating-current circuit. Mathematics See exponent. Mathematics The number of elements in a finite set. Statistics The probability of rejecting the null hypothesis where it is false. A measure of the magnification of an optical instrument, such as a microscope or telescope. Christianity The sixth of the nine orders of angels in medieval angelology. Archaic An armed force. Of or relating to political, social, or economic control: a power struggle; a power base. Operated with mechanical or electrical energy in place of bodily exertion: a power tool; power car windows. Of or relating to the generation or transmission of electricity: power companies; power lines. Informal Of or relating to influential business or professional practices: a pinstriped suit with a power tie; met with high-level executives at a power breakfast.