Pronunciation: (lOO'mu-nuns),[key] —n. 1. the state or quality of being luminous.
2. Also calledluminosity. the quality or condition of radiating or reflecting light: the blinding luminance of the sun. 3. Optics.the quantitative measure of brightness of a light source or an illuminated surface, equal to luminous flux per unit solid angle emitted per unit projected area of the source or surface.