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

Common triggers The onset of sunset anxiety could be related to the circadian rhythm, which is the body’s internal clock that regulates many functions, according to experts. —Erica Lamberg, Fox News, 26 Dec. 2024

Free-running time refers to the period in which an organism's biological clock, also known as its circadian rhythm, resets. —Michael Franco, New Atlas, 24 Dec. 2024

Your Circadian Rhythm May Influence Your Symptoms Your circadian rhythm is your body’s 24-hour internal clock. —Korin Miller, Verywell Health, 23 Dec. 2024

Developing your body’s circadian rhythm can aid in easing stress, regulating hormones, and improving mood and brain functions. —Celeste Polanco, Essence, 19 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