1. A correction to the contrast of images and displays, performed by either software or hardware, and designed to correct for the fact that the intensity displayed on a cathode-ray tube is not linearly related to the input voltage.
2. Adjustments applied during the display of a digital representation of color on a screen in order to compensate for the fact that the Cathode Ray Tubes used in computer monitors, and televisions, produce a light intensity which is not proportional to the input voltage.

The light intensity is actually proportional to the input voltage raised to the inverse power of some constant, called gamma.