Meaning of BRIGHTNESS in English
/bruyt"nis/ , n.
1. the quality of being bright.
2. Optics. the luminance of a body, apart from its hue or saturation, that an observer uses to determine the comparative luminance of another body. Pure white has the maximum brightness, and pure black the minimum brightness.
[ bef. 950; ME brihtnes, OE beorhtnes. See BRIGHT, -NESS ]
Random House Webster's Unabridged English dictionary. Полный английский словарь Вебстер - Random House . 2012