What is "dichromacy"

n. The quality of having two independent channels for conveying color information in the eye.

n. a deficiency of color vision in which the person can match any given hue by mixing only two other wavelengths of light (as opposed to the three wavelengths needed by people with normal color vision) [syn: dichromatism, dichromatopsia, dichromia, dichromasy]

Dichromacy (di meaning "two" and chroma meaning "color") is the state of having two types of functioning color receptors, called cone cells, in the eyes. Organisms with dichromacy are called dichromats. Dichromats can match any color they see with a mixture of no more than two pure spectral lights. By comparison, trichromats require three pure spectral lights to match all colors that they can perceive, and tetrachromats require four.

Dichromacy in humans is a color vision defect in which one of the three basic color mechanisms is absent or not functioning. It is hereditary and sex-linked, predominantly affecting males. Dichromacy occurs when one of the cone pigments is missing and color is reduced to two dimensions.