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
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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
With this circadian rhythm pattern in mind, researchers have been examining whether achieving better control of blood pressure overnight could be a more accurate predictor of heart health complications.
—
Emily Kay Votruba, EverydayHealth.com, 11 July 2025
The former feature offers daily suggestions for how to best get your circadian rhythm in check throughout the day.
—Kristine Thomason, Vogue, 10 July 2025
Chronotypes reveal unique sleep patterns While most people are familiar with the idea of circadian rhythms, the concept of chronotypes has only recently gained widespread attention.
—Jp Shaffer
july 7, Charlotte Observer, 7 July 2025
Human health, how exposure to light at night affects chemical reactions during our sleeping patterns, our circadian rhythm and effectively affecting melatonin cycles.
—Anthony Wood, Space.com, 2 July 2025
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Emily Kay Votruba, EverydayHealth.com, 11 July 2025
The former feature offers daily suggestions for how to best get your circadian rhythm in check throughout the day.
—Kristine Thomason, Vogue, 10 July 2025
Chronotypes reveal unique sleep patterns While most people are familiar with the idea of circadian rhythms, the concept of chronotypes has only recently gained widespread attention.
—Jp Shaffer
july 7, Charlotte Observer, 7 July 2025
Human health, how exposure to light at night affects chemical reactions during our sleeping patterns, our circadian rhythm and effectively affecting melatonin cycles.
—Anthony Wood, Space.com, 2 July 2025
See All Example Sentences for circadian
Cite this Entry
“Circadian.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/circadian. Accessed 24 Jul. 2025.
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circadian
adjective
cir·ca·di·an
(ˌ)sər-ˈkad-ē-ən, -ˈkād-; ˌsər-kə-ˈdī-ən, -ˈdē-
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