visible light: human eyes are sensitive to electromagnetic (EM) radiation with wavelengths from about 400 nm (400 x 10^-9 m) for violet light through about 700 nm (700 x 10^-9 m) for red light

infra-red (IR) radiation: electromagnetic radiation with wavelengths greater that 700 nm (700 x 10^-9 m)

ultra-violet (UV) radiation: electromagnetic radiation with wavelengths shorter that 400 nm (400 x 10^-9 m)

spectrum: the display of all the colors contained in white light

dispersion: the variation in index of refraction (or speed of light) for different frequencies of light

rainbow: the display of the colors of the spectrum due to the dispersion of light by raindrops or other mist of small water droplets

cones: the color-sensitive light detectors on the retina of the eye

rods: the low-illumination light detectors on the retina of the eye

color addition: spotlights and color television are examples of color addition

color subtraction: pigments in paints and color printing are examples of color subtraction

primary colors: the simplest colors that can be combined to make other colors. For color addition, the primary colors are red, green, and blue. For color subtraction, the primary colors are cyan, yellow, and magenta.