What does dichromatism mean?
Dichromatism is a noun with two related senses, both rooted in the idea of "twoness" applied to color. Its dominant modern sense describes a form of color vision deficiency: someone with dichromatism has only two working cone types rather than the usual three, so colors that others distinguish readily — typically reds and greens — appear alike. In this sense the word overlaps with terms like dichromacy and color blindness, and it appears mostly in scientific and medical writing. A second sense describes the condition of showing two distinct colors, as when ornithologists note the dichromatism of a bird species whose males and females differ markedly in plumage. Derived from the Greek roots di- ("two") and chroma ("color"), the word is formal and technical rather than conversational, but it offers precision that broader phrases like "being color blind" cannot match, making it valuable in discussions of vision science, genetics, and animal coloration.
The condition of having color vision based on only two of the three primary colors, owing to the absence or malfunction of one cone type.
"Protanopia and deuteranopia are both forms of dichromatism."
In clinical literature this sense is often called dichromacy or dichromatopsia.
The state of exhibiting two distinct colors, especially as a characteristic of an organism's coloration.
"The species' pronounced dichromatism makes the sexes easy to tell apart in the field."
Rarely pluralized, since the word usually denotes a general condition or property; the plural appears only when contrasting different instances or types across subjects.
"Researchers compared the dichromatisms observed across several primate species."
Some animals live in a world of just two colors — and for about 8% of men, so do we.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of dichromatism
Dichromatism derives from Greek roots: di- meaning "two" and chrōma meaning "color," combined with the English suffix -ism to denote a condition or state. The compound entered English in the nineteenth century alongside other technical vocabulary built on chroma, such as monochromatism and polychromatism. It shares its Greek ancestry with words like chromatic and chromosome, which likewise carry the root chrōma into modern scientific English.
Related word forms
How dichromatism is actually used
A technical term found mainly in scientific contexts such as optics, zoology, botany, and ophthalmology; it is uncommon in everyday conversation. In medical usage it is largely synonymous with dichromacy. When applied to organisms, it often carries the connotation of sexual dimorphism expressed through coloration.
Easily confused with dichromatism
Dichromatism refers broadly to the condition or state of having two-color vision, while dichromatopsia is a clinical term for the specific visual disorder itself.
A dichotomy is a division into two mutually exclusive parts, whereas dichromatism concerns color — either the perception of only two colors or the display of two colors.