NYCTHEMERON, the natural day, or day and night, which together always make twenty-four hours.
NYCTALOPIA, in medicine, a two-fold disorder of the eye, one of which is opposite to the other. In the first, the sight is best in the night, and in obscure places; whereas in a clear light their sight fails, so that they can hardly see any thing. In the other sort of nyctylopia, the patient can see nothing at all except in a clear and bright light.