Dichromat

Part of speech: noun

Definitions

1. A type of organism or visual system capable of distinguishing between two specific colors
2. An individual exhibiting dichromacy, which is the condition of having two types of color receptors
3. A classification in color vision where perception is limited to two distinct colors due to the absence or malfunction of certain photopigments

Etymology: A dichromat is someone who sees only two of the three primary cone signals, so the word is a technical coinage built from Greek roots rather than an old folk term. "Di-" means "two" and "chroma" means "colour," and the "-at" ending follows the pattern of scientific words for a person with a condition, as in "monochromat" and "trichromat." The formation is transparent: a dichromat has two working colour channels where a typical person has three. The word belongs to the study of colour vision, which developed in the modern era when scientists began classifying the kinds of colour blindness they could measure. Dichromacy is usually divided into types such as protanopia and deuteranopia, which affect the red-sensitive and green-sensitive cones respectively, and tritanopia, which affects the blue-sensitive cones. Each is a different kind of dichromacy, and the terms describe which cone type is missing rather than how strongly colours look muted.