lightness, <of a related colour>
brightness of an area judged relative to the brightness of a similarly illuminated area that appears to be white or highly transmitting
Note 1 to entry: Only related colours exhibit lightness.
Note 2 to entry: This entry was numbered 845-02-31 in IEC 60050-845:1987.
Note 3 to entry: This entry was numbered 17-680 in CIE S 017:2011.