density of incident radiant flux with respect to area at a point on a real or imaginary surface
Note 1 to entry: The corresponding photometric quantity is "illuminance". The corresponding quantity for photons is "photon irradiance".
Note 2 to entry: The irradiance is expressed in watt per square metre (W⋅m−2).
Note 3 to entry: This entry was numbered 845-01-37 in IEC 60050-845:1987.
Note 4 to entry: This entry was numbered 17-608 in CIE S 017:2011.