1. The condition or quality of emitting or reflecting light: The luminance of the moon in the evening enhanced the romantic nature of the garden; especially, the reflective image shining on the surface of the pond.
2. A measure of the brightness on an external area that is equal to the amount of luminous flux arriving at, passing through, or reflecting from the surface of something: The challenge for the physics students was to create a working model to measure the luminance of various light fixtures used in daily life; such as, kitchen lights, desk lights, lights on the computer, etc.

Luminance is measured in candelas per square meter. A "candela" is the basic unit of luminous intensity adopted under the Systeme International d'Unites; equal to 1/60 of the luminous intensity per square centimeter of a black body radiating at the temperature of 2,046 degrees Kelvin, or the solidification of platinum.