What is the difference between light and value?

a. light is the illumination coming from a light source, where as value is the degree of lightness or lack if light in a hue.

b. light is the brightness or dullness of a hue, where as value is the similarity that exists between a certain color and the other colors surrounding it.

c. light is the degree of lightness or lack if light in a hue, where as value is the illumination of an overall piece using monochromatic or analogous colors.

d. light is the element used by artists that directs the eye to given sections of a piece, where as value is the amount of light used in the piece as whole.