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

  • n. A visual defect characterized by the inability to see as clearly in bright light as in dim light.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. The inability to see clearly in bright light; day blindness

from the GNU version of the Collaborative International Dictionary of English

  • n. A disease of the eyes, in consequence of which a person can see clearly or without pain only by daylight or a strong artificial light; day sight.

from The Century Dictionary and Cyclopedia

  • n. In pathology, a defect of sight in consequence of which distinct vision is possible only in artificial or dim light; day-blindness. The term is also used, however, to express exactly the opposite defect of vision. See nyctalopia.

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

  • n. inability to see clearly in bright light


New Latin, from Greek hēmeralōps, suffering from hemeralopia : hēmera, day + alaos, blind + ōps, eye; see nyctalopia.
(American Heritage® Dictionary of the English Language, Fourth Edition)


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  • An autantonym, for those of you who collect 'em. This contains the element -al- "blind", so properly means "blindness by day"; but this element was neglected and it was treated as "seeing by day", synonymous with 'nyctalopia' "blindness by night". Except that the -al- was sometimes ignored in that too, so 'nyctalopia' was also used for "seeing by night".

    August 20, 2008