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

Health experts say time changes disrupt the body's circadian rhythm and release hormones. —Joey Garrison, USA TODAY, 13 Dec. 2024

Light exposure in the morning for 10 minutes can also help align with your circadian rhythm. —Maria Sokolina, Forbes, 12 Dec. 2024

As typical of vampires, Court Orlok’s nocturnal circadian rhythm means much of the film takes place in the dead of night, with characters bathed in blueish moonlight. —Leah Dolan, CNN, 11 Dec. 2024

Their argument: Shifting sunlight later in the day contradicts the body’s circadian rhythms. —Mary Ellen Klas, Twin Cities, 11 Dec. 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