di·​ur·​nal | \ dī-ˈər-nᵊl How to pronounce diurnal (audio) \

Definition of diurnal

 (Entry 1 of 2)

1a biology : active chiefly in the daytime diurnal animals
b : of, relating to, or occurring in the daytime the city's diurnal noises
c botany : opening during the day and closing at night diurnal flowers
2a : recurring every day diurnal tasks
b : having a daily cycle diurnal tides



Definition of diurnal (Entry 2 of 2)

2 archaic : diary, daybook

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Other Words from diurnal


diurnally \ dī-​ˈər-​nᵊl-​ē How to pronounce diurnally (audio) \ adverb

Examples of diurnal in a Sentence


a love as constant and certain as the diurnal tides


a microfilm containing a collection of diurnals published by 19th-century American abolitionists

Recent Examples on the Web: Adjective

Under the new law, which takes effect in 90 days, pet dealers are required to regularly groom animals to prevent matting and flea and tick infestations and provide animals with diurnal lighting cycles, which mimic natural, 24-hour light patterns. USA TODAY, "Smokey Bear, tarantula trek, censoring Adam and Eve: News from around our 50 states," 9 Aug. 2019 Passive house systems work really well in climates with big diurnal temperature swings, like the desert. New York Times, "Do Americans Need Air-Conditioning?," 3 July 2019 That diurnal cycle is linked to the giant impact by a fundamental law of physics, the conservation of angular momentum. Simon J. Lock, Scientific American, "When Earth and the Moon Were One," 2 July 2019 These sorts of scenes seem to create a theater set across which Tillim’s subjects move, like characters enacting a diurnal purpose. Carole Naggar, The New York Review of Books, "Framing Time: Guy Tillim’s African Street Photography," 25 May 2019 By analyzing coyote scat, scientists have linked this behavioral change to dietary shifts from diurnal to nocturnal prey, with implications for small mammal communities and for competition with other predators. Kaitlyn Gaynor, CNN, "To avoid humans, more wildlife now work the night shift," 14 June 2018 That leaves her beachside club almost the entire day to entertain the diurnal, even if that’s the only trait some of her patrons have in common. New York Times, "You Can’t Hurt Lindsay Lohan Now," 26 June 2018 Sun bears, for example, are typically diurnal and sun-loving creatures; in undisturbed areas less than 20% of their activity occurred at night. Kaitlyn Gaynor, CNN, "To avoid humans, more wildlife now work the night shift," 14 June 2018 That’s the conclusion of a new study, which shows that a variety of previously diurnal animals such as foxes, deer, and boars have become nocturnal to avoid human activity out of fear. Elizabeth Gamillo, Science | AAAS, "Human activity is causing more and more animals to embrace the night," 14 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'diurnal.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of diurnal


14th century, in the meaning defined at sense 2a


1600, in the meaning defined at sense 2

History and Etymology for diurnal

Adjective and Noun

Middle English, from Latin diurnalis — more at journal

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Statistics for diurnal

Last Updated

17 Sep 2019

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Time Traveler for diurnal

The first known use of diurnal was in the 14th century

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English Language Learners Definition of diurnal

: active mainly during the day
: happening every day


di·​ur·​nal | \ dī-ˈərn-ᵊl How to pronounce diurnal (audio) \

Medical Definition of diurnal

1 : having a daily cycle diurnal rhythms
2a : of, relating to, or occurring in the daytime diurnal activity
b : chiefly active during the daytime diurnal mosquitoes

Other Words from diurnal

diurnally \ -​ᵊl-​ē How to pronounce diurnally (audio) \ adverb

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More from Merriam-Webster on diurnal

Rhyming Dictionary: Words that rhyme with diurnal

Thesaurus: All synonyms and antonyms for diurnal

Spanish Central: Translation of diurnal

Nglish: Translation of diurnal for Spanish Speakers

Britannica English: Translation of diurnal for Arabic Speakers

Comments on diurnal

What made you want to look up diurnal? Please tell us where you read or heard it (including the quote, if possible).


miscellaneous remnants or debris

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