[ 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

Can be confused

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

Examples from the Web for nocturnal

British Dictionary definitions for nocturnal


/ (nɒkˈtɜːnəl) /


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, 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

Medicine definitions for nocturnal


[ nŏk-tûrnəl ]


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.

Science definitions for nocturnal


[ nŏk-tûrnəl ]

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.