dichromatism
(daɪˈkrəʊmətɪz(ə)m)
[f. as prec.: see -ism.]
1. The quality or fact of being dichromatic.
| 1884 Coues Key to N.A. Birds (ed. 2) 656 Remarkable differences of plumage in many cases, constituting dichromatism, or permanent normal difference in color. |
2. Ophthalm. Defective colour vision in which only two (rather than three) pure colours, in different combinations, are sufficient to produce a colour indistinguishable from any perceived.
| 1909 in Webster. 1910 Proc. R. Soc. B. LXXXII. 463 The defect which has caused the non-perception of certain red rays has not caused the dichromatism. 1959 New Scientist 30 Apr. 972/2 In dichromatism, the colour-blind subject requires only two primaries in order to match any spectral colour. |