nyctalopia |ˌnɪkˈtlɑːpɪk| — inability to see clearly in dim light; due to a deficiency of vitamin A or to a retinal disorder

nyctalopic  — (medicine) Unable to see clearly in low light; night-blind; suffering from nyctalopia.

nylghau |ˈnɪlɡɔː| — large Indian antelope; male is blue-grey with white markings; female is brownish with no horns

nylon |ˈnaɪlɑːn| — a thermoplastic polyamide; a family of strong resilient synthetic fibers

nymph |nɪmf| — (classical mythology) a minor nature goddess usually depicted as a beautiful maiden

nystagmus |nəˈstaɡməs| — involuntary movements of the eyeballs; its presence or absence is used to diagnose a variety of neurological and visual disorders