power

In mathematics, that which is represented by an exponent or index, denoted by a superior numeral. A number or symbol raised to the power of 2 – that is, multiplied by itself – is said to be squared (for example, 3², x²), and when raised to the power of 3, it is said to be cubed (for example, 2³, y³). Any number to the power zero always equals 1.

Powers can be negative. Negative powers produce fractions, with the numerator as one, as a number is divided by itself, rather than being multiplied by itself, so for example 2⁻¹ = 1/2 and 3⁻³ = 1/27.

power

In physics, the rate of doing work or transferring energy from one form to another. It is measured in watts (joules per second) or other units of work per unit time.

power

In optics, a measure of the amount by which a lens will deviate light rays. A powerful converging lens will converge parallel rays strongly, bringing them to a focus at a short distance from the lens. The unit of power is the dioptre, which is equal to the reciprocal of focal length in metres. By convention, the power of a converging (or convex) lens is positive and that of a diverging (or concave) lens negative.