Contrast ratio
When referring to a display, the contrast ratio is a figure used to measure the luminance difference between the brightest white and the darkest black. The contrast ratio will be listed as y:z where 'y' is the brightest white and 'z' is the darkest black. An example of a standard contrast ratio for computer monitors and LCD displays is 200:1, a number higher than this, such as 600:1, will have a brighter display.
Also see: Contrast, Luminance, Video definitions