The brightness of a color based on a scale from black to white on your monitor.
Or brightness; In astronomy, the amount of light emitted by a star, measured in magnitudes. The apparent brightness of an object decreases in proportion to the square of its distance from the observer. The luminosity of a star or other body can be expressed in relation to that of the Sun.The quality of being luminous; emitting or reflecting light; SYN. brightness, luminance, luminousness, light.