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Definition of circadian
: being, having, characterized by, or occurring in approximately 24-hour periods or cycles (as of biological activity or function) circadian rhythms in activity
From the M-W Editors
circadian was our Word of the Day on 06/27/2010. Hear the podcast!
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Recent Examples of circadian from the Web
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Purpose: Exposure to natural light helps maintain circadian rhythms for babies, parents and staff, and views of nature reduce stress and anxiety.
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Scientists attribute these effects to our circadian rhythm, the body’s 24-hour clock, which causes body temperature to rise slightly throughout the day and peak in late afternoon.
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One of the key markers of the circadian clock is melatonin.
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The bulbs change color throughout the day to provide different types of light matching the body’s circadian rhythms, which determine when people should wake, work and rest.
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Melatonin, produced by the body, synchronizes circadian rhythms and helps promote sleep.
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According to the National Institute of General Medical Sciences, circadian rhythms are physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism's environment.
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Blue light is known to suppress melatonin production, a hormone that is key to the sleep-wake cycle, known as the circadian rhythm.
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But there’s one app that focuses on your circadian rhythm, which might be the most important part of your nocturnal experience.
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'circadian'. Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
Did You Know?
Just over fifty years ago, no one talked about "circadian rhythms" - because "circadian" hadn't even been coined yet. In 1959, a scientist formed the word from the Latin words circa ("about") and "dies" ("day"), and it caught on quickly. "Circadian" appeared in periodicals throughout the sixties, and appeared in a Merriam-Webster dictionary before the decade was up. 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."
Origin and Etymology of circadian
Latin circa about + dies day + English 2-an — more at deity
Other Physiology Terms
CIRCADIAN Defined for English Language Learners
circadian
playDefinition of circadian for English Language Learners
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: relating to the regular changes in a person or thing that happen in 24-hour periods
Medical Dictionary
circadian
playMedical Definition of circadian
Learn More about circadian
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See words that rhyme with circadian Britannica English: Translation of circadian for Arabic speakers
Seen and Heard
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