What is saturation?

saturation 

1. See SATURATION POINT. 2. The state of purity of a color. In
general, the greater the saturation, the narrower the bandwidth of
the electromagnetic energy. The highest possible saturation is represented by energy at a single wavelength [e.g., light of 700 nanometers (nm) appears as highly saturated red, and light of 400 nm appears as highly saturated violet]. Compare HUE. 3. The condition of a ferromagnetic material in which it can accommodate no additional magnetic flux. 4. The condition of a dielectric material in which it can accommodate no additional electric flux.