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

Physical activity can also help to prevent nighttime wandering, a common danger among Alzheimer’s patients due to dysfunction in their circadian rhythms, according to Sherri Snelling, a gerontologist and spokesperson for Comfort Keepers in California. —Melissa Rudy, Fox News, 8 Nov. 2024

Shift workers often work at schedules that are misaligned with the circadian rhythm of the human body. —Lieke Ten Brummelhuis, Forbes, 5 Nov. 2024

Our body’s internal clock, or circadian rhythm, regulates our sleep-wake cycles. —Anita Bhagwandas, Condé Nast Traveler, 29 Oct. 2024

Melatonin is a hormone made by our bodies' pineal gland that helps regulate our circadian rhythms, the natural patterns our bodies experience in a 24-hour cycle. —Michael Franco, New Atlas, 4 Nov. 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