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 (sər-kā′dē-ən, -kăd′ē-, sûr′kə-dī′ən, -dē′-)
adj. Biology
Relating to or exhibiting approximately 24-hour periodicity.

[Latin circā, around; see circa + Latin diēs, day; see dyeu- in Indo-European roots.]

cir·ca′di·an·ly adv.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Biology) of or relating to biological processes that occur regularly at about 24-hour intervals, even in the absence of periodicity in the environment. See also biological clock
[C20: from Latin circa about + diēs day]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(sɜrˈkeɪ di ən, ˌsɜr kəˈdi ən)

of or pertaining to rhythmic cycles recurring at approximately 24-hour intervals: the circadian biological clock.
[1955–60; < Latin circā about + di(ēs) day + -an1]
cir•ca′di•an•ly, adv.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Adj.1.circadian - of or relating to biological processes occurring at 24-hour intervals; "circadian rhythms"
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.


[səˈkeɪdɪən] ADJcircadiano
circadian cycleciclo m circadiano
Collins Spanish Dictionary - Complete and Unabridged 8th Edition 2005 © William Collins Sons & Co. Ltd. 1971, 1988 © HarperCollins Publishers 1992, 1993, 1996, 1997, 2000, 2003, 2005


adj circadiano; — rhythm ritmo circadiano
English-Spanish/Spanish-English Medical Dictionary Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.
References in periodicals archive ?
ENPNewswire-August 2, 2019--University College Cork: Tick-Tock of the Circadian Clock: UCC exhibition to explore biological time
Researchers have long been searching for ways to understand and address this link, and a study published in Scientific Reports adds a new piece to the puzzle: the circadian rhythm.
Researchers in Switzerland compiled studies, predominantly in mice, that looked at the connection between circadian rhythms and immune responses.
A new study investigating why they work concludes that circadian rhythms are key.
A new research suggests that a gene that governs the body's circadian clock acts differently in males as compared to females and may protect females from heart disease.
The idea that our waking and sleep cycles operate according to an internal clock called the circadian clock has been around for centuries, but it's only been in the past few decades that we are learning the circadian clock does much more than control sleep.
Participants lived in a facility under dim light conditions (10 lux measured from the forehead), ate three meals at set times, and followed a strict sleeping schedule: "To adjust the sleep-wake cycle among the subjects in reference to the circadian cycle, the times of retiring to bed and wake-up were fixed in such a way that the retirement time should be 4 h before the melatonin peak and sleep length should be 8 h." Blood samples, from an indwelling catheter in the forearm, were taken hourly during the first and last 24 hours and every two hours for the remainder of the study to examine the circadian peak phase of plasma melatonin.
WEDNESDAY, July 11, 2018 (HealthDay News) -- The endogenous circadian system, behavioral cycle, and circadian misalignment have distinct effects on insulin sensitivity and ?-cell function, according to a study published online June 4 in Diabetes, Obesity and Metabolism.
Young "for their discoveries of molecular mechanisms controlling the circadian rhythm." The Nobel Assembly declared on October 02, 2017 that the winners "were able to peek inside our biological clock and elucidate its inner workings".1
The third cycle is the circadian rhythm, or cycles that last for a day, such as the sleep/wake cycle.
Most organisms express daily rhythms of activity and physiology that persist in constant conditions and thus are referred to as circadian rhythms.