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[nok-tur-nl] /nɒkˈtɜr nl/
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 forms
nocturnality, noun
nocturnally, adverb
nonnocturnal, adjective
nonnocturnally, adverb
seminocturnal, adjective
unnocturnal, adjective
unnocturnally, adverb
Can be confused
diurnal, nocturnal.
2. nighttime. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for nocturnal
Contemporary Examples
Historical Examples
  • 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.

    The Devil's Dictionary Ambrose Bierce
  • 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.

    A Waif of the Mountains Edward S. Ellis
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 Forms
nocturnality, noun
nocturnally, adverb
Word Origin
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
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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
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nocturnal in Medicine

nocturnal noc·tur·nal (nŏk-tûr'nəl)

  1. Of, relating to, or occurring in the night.

  2. Most active at night.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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nocturnal in Science
  1. Occurring at night.

  2. Most active at night. Many animals, such as owls and bats, are nocturnal.

  3. 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 © 2002. Published by Houghton Mifflin. All rights reserved.
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