circadian
Say it: sur-KAY-dee-un /səːˈkeɪdɪən/ · adjective
What “circadian” means
Following the body's roughly daily rhythm.
More precisely: Relating to the body's roughly 24-hour internal clock that governs sleep and alertness.
Example: “Morning sunlight helps reset your circadian rhythm after a long-haul flight.”
When to use it
In biology or sleep discussions, to describe internal daily cycles in sleep, alertness and other body functions.
Memory trick
Latin circa means about and dies means day: circadian means about a day.
Similar words
daily, diurnal, cyclical
Where it comes from
From Latin circa 'about' + dies 'day'.
Quick check
Even without checking the time, you become sleepy at a similar hour each evening. That internal rhythm is…
seasonal or circadian?
Show the answer
circadian
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