Black is at the end of the achromatic axis in the various color models. In the grayscale, black has the lowest value at 0%, just as it has the value "0" in the Munsell scale.
Indigital video technology, there is ultrasonic black. This is the signal area of a digital video signal below 0% white. This area is also called footroom. In English, this area is called "Blacker than Black".