of or relating to the night (opposed to diurnal).
done, occurring, or coming at night: nocturnal visit.
active at night (opposed to diurnal): nocturnal animals.
opening by night and closing by day, as certain flowers (opposed to diurnal).


Archaic. an astrolabe for telling time at night or for determining latitude by the position of certain stars in reference to Polaris.

Origin of nocturnal

From the Late Latin word nocturnālis, dating back to 1475–85. See nocturn, -al1
Related formsnoc·tur·nal·i·ty, nounnoc·tur·nal·ly, adverbnon·noc·tur·nal, adjectivenon·noc·tur·nal·ly, adverbsem·i·noc·tur·nal, adjectiveun·noc·tur·nal, adjectiveun·noc·tur·nal·ly, adverb
Can be confuseddiurnal nocturnal

Synonyms for nocturnal Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Related Words for nocturnal

nightly, nighttime, late, night

Examples from the Web for nocturnal

Contemporary Examples of nocturnal

  • As the sun was setting, we made our way back, along a highway furrowed by hippos during their nocturnal forages.

  • Coffeehouses stayed open late, while in the countryside, “spinning bees”—nocturnal gatherings of women—were enduringly popular.

    The Daily Beast logo
    The Best of Brit Lit

    Peter Stothard

    October 12, 2011

  • Dennis was recovering from a downturn in his life—wild drugs, hospital, and a nocturnal escape organized by Jack Nicholson.

    The Daily Beast logo
    Remembering My Friend Dennis

    Caroline Graham

    May 29, 2010

  • With our long immigration stalemate, it is currently, and perhaps eternally, a nocturnal river.

    The Daily Beast logo
    My Night on the Border

    Bryan Curtis

    May 25, 2010

  • I will admit, however, they made for some spectacular views of nocturnal Baghdad in its orange bath of streetlights.

    The Daily Beast logo
    Commuting to Iraq

    Kyle McEneaney

    March 21, 2009

Historical Examples of nocturnal

  • Wretched about one son, he was dismayed at the nocturnal visit of the other.

    Weighed and Wanting

    George MacDonald

  • It was nocturnal in its habits, and somewhat addicted to dancing and the theft of children.

  • Do not they sometimes favour the world with these nocturnal shriekings?

    Vivian Grey

    Earl of Beaconsfield, Benjamin Disraeli

  • Have you come to pay us a nocturnal visit, or—there's nothing the matter?

    A Spirit in Prison

    Robert Hichens

  • But Vose was not yet through with his nocturnal experiences.

British Dictionary definitions for nocturnal



of, used during, occurring in, or relating to the night
(of animals) active at night
(of plants) having flowers that open at night and close by day
Compare diurnal
Derived Formsnocturnality, nounnocturnally, adverb

Word Origin for nocturnal

C15: from Late Latin nocturnālis, from Latin nox night
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

Word Origin and History for nocturnal

late 15c., from Old French nocturnal "nightly, nocturnal," or directly from Late Latin nocturnalis, from Latin nocturnus "belonging to the night," from nox (genitive noctis) "night," cognate with Old English neaht (see night) + -urnus, suffix forming adjectives of time. Nocturnal emission "involuntary ejaculation during sleep" first recorded 1813.

Online Etymology Dictionary, © 2010 Douglas Harper

nocturnal in Medicine




Of, relating to, or occurring in the night.
Most active at night.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

nocturnal in Science



Occurring at night.
Most active at night. Many animals, such as owls and bats, are nocturnal.
Having flowers that open during the night and close at daylight. Nocturnal plants are often pollinated by moths. Compare diurnal.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.