irradiance

English

Etymology tree

English irradiant

Proto-Indo-European *-onts

Latin -ns

Latin -āns

Proto-Indo-European *-(i)yós

Proto-Italic *-ijos

Proto-Italic *-ios

Old Latin -ios

Latin -ius

Latin -ia

Latin -āntia

Old French -ancebor.

Middle English -aunce

English -ance

English irradiance

English Wikipedia has an article on:

irradiance

Wikipedia

irradiance (countable and uncountable, plural irradiances)

The act of irradiating; emission of rays of light.
That which irradiates or is irradiated; lustre; splendour; brilliancy.
(physics) The radiant power received by unit area of surface.
- 1959, United States. National Aeronautics and Space Administration, NASA Technical Note (issues 3641-3650, page 15)
  The geometry of the cone θ and the irradiance at the image of the carbon block were used to determine the absolute steradiancy of the energy in the cone θ as a radiometer calibration value.

The act of irradiating

That irradiates or is irradiated

physics: Radiant power received by unit area of surface