Definition of diurnal adjective from the Oxford Advanced Learner's Dictionary



    BrE BrE//daɪˈɜːnl//
    ; NAmE NAmE//daɪˈɜːrnl//
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  1. 1(biology) (of animals) active during the day Unlike most other bats, this species is diurnal. opposite nocturnal
  2. 2(astronomy) taking one day the diurnal rotation of the earth
  3. Word Originlate Middle English (as a term in astronomy): from late Latin diurnalis, from Latin diurnus ‘daily’, from dies ‘day’.
See the Oxford Advanced American Dictionary entry: diurnal