circadian

adjective

cir·​ca·​di·​an sər-ˈkā-dē-ən 

: being, having, characterized by, or occurring in approximately 24-hour periods or cycles (as of biological activity or function)

circadian rhythms in activity

Did you know?

In 1959, a scientist formed the word circadian from the Latin words circa ("about") and dies ("day"), and it caught on quickly. Most often, it's seen and heard in the term circadian rhythm, which refers to the inherent cycle of about 24 hours that appears to control various biological processes, such as sleep, wakefulness, and digestive activity. If you want to impress your friends, you can also use the term circadian dysrhythmia, a fancy synonym of jet lag.

Examples of circadian in a Sentence

Recent Examples on the Web

These include understanding circadian rhythms, learning what foods boost sleep cycles and practicing meditation. —Ramsey Qubein, Forbes, 30 Mar. 2024

Also, make note of other factors around your workout that might make a difference—for example, light, which strongly influences circadian rhythms. —Cindy Kuzma, SELF, 27 Mar. 2024

Bathing, as well as being a relaxing ritual in itself, is a great way to raise body temperature and in turn kick start the body’s circadian rhythm to get it back on a more regular footing. —Georgia Day, Vogue, 27 Mar. 2024

Studies suggest that people who have poor sleep patterns or work night shifts, disrupting their circadian rhythms, may have a higher risk of developing various types of cancer. —Dominique Fluker, Essence, 22 Mar. 2024

Bullough told The Star that while the blue family of visible light can have negative impacts on eye health and circadian rhythms over time at a high intensity, the light emanating from defective streetlights is nowhere near strong enough to affect humans’ health. —Natalie Wallington, Kansas City Star, 22 Mar. 2024

Magnesium also helps balance hormones related to sleep and circadian rhythm, decreases migraine headaches, and helps regulate mood. —Allison Futterman, Discover Magazine, 18 Mar. 2024

Research has shown that RLS may happen at night due to a link between the sleep/wake cycle (circadian rhythm) and the nervous system. —Health Editorial Team, Health, 15 Mar. 2024

Early start times are particularly problematic for teens whose circadian rhythms naturally drift later. —TIME, 9 Mar. 2024

Word History

Etymology

Latin circa about + dies day + English -an entry 2 — more at deity

First Known Use

1959, in the meaning defined above

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Medical Definition

circadian

adjective

cir·​ca·​di·​an (ˌ)sər-ˈkad-ē-ən, -ˈkād-; ˌsər-kə-ˈdī-ən, -ˈdē- 

: being, having, characterized by, or occurring in approximately 24-hour periods or cycles (as of biological activity or function)

circadian periodicity

circadian rhythms in behavior or physiological activity

compare infradian, ultradian