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Synonyms

diurnal

American  
[dahy-ur-nl] / daɪˈɜr nl /

adjective

  1. of or relating to a day or each day; daily.

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

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

  4. active by day, as certain birds and insects (nocturnal ).

noun

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

  2. Archaic. a diary.

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

diurnal British  
/ daɪˈɜːnəl /

adjective

  1. happening during the day or daily

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

  3. (of animals) active during the day Compare nocturnal

"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

noun

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

"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
diurnal Scientific  
/ dī-ûr′nəl /

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

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

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

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

  4. Compare nocturnal

Other Word Forms

  • diurnally adverb
  • diurnalness noun
  • transdiurnal adjective
  • undiurnal adjective
  • undiurnally adverb

Etymology

Origin of diurnal

1400–50; late Middle English < Latin diurnālis, equivalent to diurn ( us ) daily + -ālis -al 1

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

These huge swings are known as the diurnal temperature range.

From BBC • Mar. 19, 2026

Wilder’s drama, offering a guided tour of an ordinary town going about its diurnal business, reminds us, through the inescapable shadow of mortality, of what we have in common.

From Los Angeles Times • Nov. 12, 2024

Yellow-bellied marmots are an excellent study system because they are diurnal, or active during the day, and they have an address.

From Salon • Oct. 23, 2024

The 12 diurnal tiger beetle species that the researchers included in the study are evidence of this.

From Science Daily • May 15, 2024

They trade normal diurnal rhythms for the perk of having very little inmate contact—at night, all the inmates are locked in their cells.

From "Newjack: Guarding Sing Sing" by Ted Conover

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.