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
Research also shows that circadian rhythms can impact men and women differently, with women experiencing greater cognitive impairments at night.
—
Mark Travers, Forbes.com, 5 June 2025
That’s because exposure to natural light is imperative to the operation of your body’s circadian rhythm, or internal clock.
—CNN Money, 5 June 2025
Light-emitting devices affect the body’s melatonin levels and circadian rhythm (the body's natural 24-hour internal clock).
—Carrie Madormo, Verywell Health, 3 June 2025
This soft lighting doesn't disturb circadian rhythms or sleep patterns.
—Nafeesah Allen, Better Homes & Gardens, 29 May 2025
See All Example Sentences for circadian
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Mark Travers, Forbes.com, 5 June 2025
That’s because exposure to natural light is imperative to the operation of your body’s circadian rhythm, or internal clock.
—CNN Money, 5 June 2025
Light-emitting devices affect the body’s melatonin levels and circadian rhythm (the body's natural 24-hour internal clock).
—Carrie Madormo, Verywell Health, 3 June 2025
This soft lighting doesn't disturb circadian rhythms or sleep patterns.
—Nafeesah Allen, Better Homes & Gardens, 29 May 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 10 Jun. 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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