Definition: In traditional preparation of color separations, a red keyline on the black line art marked the outline of solid or tint color areas. In some cases a black keyline was used when it served as both a color indicator and an outline to be printed in black.
Because usually the black plate (black ink) contained the keyline, the K in CMYK represents the keyline or black plate also sometimes called the key plate.
Also see: What Does a Keyliner Do?
Also Known As: key
