radiance

noun

1. radiant brightness or light: the radiance of the tropical sun.
2. warm, cheerful brightness: the radiance of her expression.
3. Rare. radiation.

noun plural -ances or -ancies

1. the quality or state of being radiant
2. a measure of the amount of electromagnetic radiation leaving or arriving at a point on a surface. It is the radiant intensity in a given direction of a small element of surface area divided by the orthogonal projection of this area onto a plane at right angles to the directionSymbol: L e

n.

c.1600, “brilliant light,” from radiant or else from Medieval Latin radiantia “brightness,” from radiare “to beam, shine” (see radiation). Figurative use from 1761. Related: Radiancy.

n.

1. The quality or state of being radiant.
2. The radiant energy emitted per unit time in a specified direction by a unit area of an emitting surface.