radiance -
The quality of being radiant, shining, bright or splendid.
radiance -
The flux of radiation emitted per unit solid angle in a given direction by a unit area of a source.
Wikipedia
Radiance and spectral radiance are radiometric measures that describe the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle in a specified direction. They are used to characterize both emission from diffuse sources and reflection from diffuse surfaces. The SI unit of radiance is watts per steradian per square metre (W·sr·m).
OmegaWiki Dictionary
Ω
radiance A radiometric measure that describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle in a specified direction.