Lightness
Luminance: the level of visual sensation produced by brightness depending on the observation conditions
Source: "GOST 26824-2010. Interstate Standard. Buildings and Structures. Methods for Measuring Brightness"
(introduced into force by Order of Rosstandart dated 19.04.2011 No. 49-st)
Luminance: the property of visual sensation, due to which an object appears to transmit or scatter more or less significant part of the light falling on it; psychophysically this property is close to the photometric quantity - brightness coefficient
Source: "GOST R 50574-2002. Vehicles, Buses and Motorcycles of Operational Services. Colorgraphic Schemes, Identification Marks, Inscriptions, Special Light and Sound Signals. General Requirements"
(adopted by the Decision of the State Standard of Russia dated 15.12.2-st)