from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A visual defect characterized by the inability to discern blue and yellow.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A form of color blindness. The person's retina does not respond to the blue color, due to lack of "blue" cone opsins.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. rare form of dichromacy characterized by a lowered sensitivity to blue light resulting in an inability to distinguish blue and yellow


Greek tritos, third; see trei- in Indo-European roots + Greek anōpiā, blindness (an-, not; see a-1 + -ōpiā, -opia), so called because blue is considered the third of the primary colors.
(American Heritage® Dictionary of the English Language, Fourth Edition)



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