Irradiance

{ Ir‐ra″di‐ance (ĭr‐rā″dĭ‐ans), Ir‐ra″di‐an‐cy (–an‐sy̆), } n. [From Irradiant.]

1. The act of irradiating; emission of rays of light.

2. That which irradiates or is irradiated; luster; splendor; irradiation; brilliancy. Milton.