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
They are evolutionarily wired for risk-taking during teenage years as their circadian rhythms shift and reward systems develop.
—
Rachel Hale, USA Today, 26 Mar. 2025
Your circadian rhythm — the cycle that regulates sleep, hormone release and temperature — might be out of whack.
—Andrew Torgan, CNN, 23 Mar. 2025
This will anchor your sleep/wake cycle, called your circadian rhythm.
—Julio Fernandez-Mendoza, The Conversation, 20 Mar. 2025
To assess sleep patterns, participants wore wrist devices that tracked their sleep duration, quality, and circadian rhythm patterns for three days at the start and end of the study.
—Thomas G. Moukawsher, Newsweek, 20 Mar. 2025
See All Example Sentences for circadian
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Rachel Hale, USA Today, 26 Mar. 2025
Your circadian rhythm — the cycle that regulates sleep, hormone release and temperature — might be out of whack.
—Andrew Torgan, CNN, 23 Mar. 2025
This will anchor your sleep/wake cycle, called your circadian rhythm.
—Julio Fernandez-Mendoza, The Conversation, 20 Mar. 2025
To assess sleep patterns, participants wore wrist devices that tracked their sleep duration, quality, and circadian rhythm patterns for three days at the start and end of the study.
—Thomas G. Moukawsher, Newsweek, 20 Mar. 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 30 Mar. 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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