[ dahy-ur-nl ]
See synonyms for diurnal on Thesaurus.com
  1. of or relating to a day or each day; daily.

  2. of or belonging to the daytime (opposed to nocturnal).

  1. Botany. showing a periodic alteration of condition with day and night, as certain flowers that open by day and close by night.

  2. active by day, as certain birds and insects (opposed to nocturnal).

  1. Liturgy. a service book containing offices for the daily hours of prayer.

  2. Archaic. a diary.

  1. Archaic. a newspaper, especially a daily one.

Origin of diurnal

1400–50; late Middle English <Latin diurnālis, equivalent to diurn(us) daily + -ālis-al1

Other words from diurnal

  • di·ur·nal·ly, adverb
  • di·ur·nal·ness, noun
  • trans·di·ur·nal, adjective
  • un·di·ur·nal, adjective
  • un·di·ur·nal·ly, adverb

Words that may be confused with diurnal

Words Nearby diurnal

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use diurnal in a sentence

British Dictionary definitions for diurnal


/ (daɪˈɜːnəl) /

  1. happening during the day or daily

  2. (of flowers) open during the day and closed at night

  1. (of animals) active during the day: Compare nocturnal

  1. a service book containing all the canonical hours except matins

Origin of diurnal

C15: from Late Latin diurnālis, from Latin diurnus, from diēs day

Derived forms of diurnal

  • diurnally, adverb

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for diurnal


[ dī-ûrnəl ]

    • Occurring once in a 24-hour period; daily.

    • Having a 24-hour cycle. The movement of stars and other celestial objects across the sky are diurnal.

  1. Most active during the daytime. Many animals, including the apes, are diurnal.

  1. Having leaves or flowers that open in daylight and close at night. The morning glory and crocus are diurnal. Compare nocturnal.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.