circadian

C3I1R1C3A1D2I1A1N1
UK/səˈkeɪ.dɪ.ən/US/sɚˈkeɪ.di.ən/US/sɚˈkæd.i.ən/US/ˌsɝ.kəˈdi.ən/

adjective

Of, relating to, or showing rhythmic behaviour with a period of approximately 24 hours; especially of a biological process.

Similar
hemeralnyctohemeraldiurnalquotidiandailynychthemeralper diem
OriginLatin diēs ← Proto-Italic *djous ← Proto-Indo-European *dyḗws →
Less commonScrabble 14
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Word of the Day · Sep 6, 2023

Meanings

adjectivecircadian (not comparable)
  1. not comparablebiologyOf, relating to, or showing rhythmic behaviour with a period of approximately 24 hours; especially of a biological process.

    The most obvious circadian rhythm is the daily cycle of sleep and activity.

    2005, Paul Martin, Counting Sheep: The Science and Pleasures of Sleep and Dreams, page 114
    4 more examples

    The circadian clock is involved in the regulation of the diurnal sleep-wake cycle, […].

    2000, Arnold Sameroff, et al: Handbook of Developmental Psychopathology, page 310

    To summarize, the circadian system, particularly the SCN, controls the circadian pattern of melatonin release in mammals.

    2002, Jill B. Becker, Behavioral Endocrinology, page 483

    Circadian clocks developed early in evolution in single-celled organisms, before the animal and plant kingdom split from one another. The original clocks probably functioned to protect the cells from damage induced by high UV radiation.

    2014 April 5, “Quite interesting: A quietly intriguing column from the brains behind QI, the BBC quiz show. This week; QI orchids you not”, in The Daily Telegraph (Weekend), page W22

    In addition, the truck driver’s schedule involved sleeping at irregular times, including times when the body’s circadian rhythms are geared toward being awake. He was also awake at times when his circadian rhythms were geared toward being asleep. The time of the crash, about 1:36 a.m., is when sleepiness tends to be greater and performance capabilities are lower.

    2024, NTSB, Highway Investigation Report, HIR-24-05

    Synonyms: hemeral, nyctohemeral, diurnal, quotidian, daily, diurnal, hemeral, nychthemeral

Synonyms & antonyms

adjectiveOf, relating to, or showing rhythmic behaviour with a period of approximately 24 hours; especially of a biological process.

Similar
hemeralnyctohemeraldiurnalquotidiandailydiurnalhemeralnychthemeralper diemquotidian
Also see
dailydiurnaleverydayquotidian

Origin

  1. Proto-Indo-European*(s)ker-
  2. Ancient Greekκίρκος (kírkos)
  3. Latincircus
  4. Latincircum
  5. Latincircā
  6. Proto-Indo-European*dyew-
  7. Proto-Indo-European*dyḗws
  8. Proto-Italic*djous
  9. Latindiēs
  10. Englishcircadian

From Latin circā (“around”) + diēs (“day”) + English -an. Compare circannual.

Full word history & related roots →

Translations

Catalan circadiari
  • circadiarirelating to rhythmic behavior with a period of 24 hours
French circadien
  • circadienrelating to rhythmic behavior with a period of 24 hours
German circadian, zirkadian
  • circadianrelating to rhythmic behavior with a period of 24 hours
  • zirkadianrelating to rhythmic behavior with a period of 24 hours
Greek κιρκάδιος
  • κιρκάδιος (kirkádios)relating to rhythmic behavior with a period of 24 hours
Icelandic dægur-, sólarhrings-
  • dægur-relating to rhythmic behavior with a period of 24 hours
  • sólarhrings-relating to rhythmic behavior with a period of 24 hours
Irish laethúil
  • laethúilrelating to rhythmic behavior with a period of 24 hours
Italian circadiano
  • circadianorelating to rhythmic behavior with a period of 24 hours
Japanese 晦日
  • 晦日 (kaijitsu)relating to rhythmic behavior with a period of 24 hours
Polish całodobowy, dwudziestoczterogodzinny
  • całodobowyrelating to rhythmic behavior with a period of 24 hours
  • dwudziestoczterogodzinnyrelating to rhythmic behavior with a period of 24 hours
Russian циркадный, циркадианный
  • циркадный (cirkadnyj)relating to rhythmic behavior with a period of 24 hours
  • циркадианный (cirkadiannyj)relating to rhythmic behavior with a period of 24 hours
Slovak denný, cirkadiálny
  • dennýrelating to rhythmic behavior with a period of 24 hours
  • cirkadiálnyrelating to rhythmic behavior with a period of 24 hours
  • cirkadiánnyrelating to rhythmic behavior with a period of 24 hours
Spanish circadiano
  • circadianorelating to rhythmic behavior with a period of 24 hours
Ukrainian цирка́дний
  • цирка́дний (cyrkádnyj)relating to rhythmic behavior with a period of 24 hours

Rhymes & wordplay

Anagrams

cardician
Cite this entry
APA

circadian. (n.d.). In WatkinsX Dictionary. Retrieved November 3, 2026, from https://dictionary.watkinsx.com/word/circadian

MLA

“circadian.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/circadian. Accessed November 3, 2026.

Chicago

WatkinsX Dictionary, s.v. “circadian,” accessed November 3, 2026, https://dictionary.watkinsx.com/word/circadian.

Source: circadian on Wiktionary, CC BY-SA 4.0.