English Reference

Word

circadian

Phoneticscir·ca·di·an

US/sɝˈkeɪdiən/

UK/sɜːkˈeɪdiən/

Definition

adj. relating to a natural daily cycle of about twenty-four hours. You use this to describe things like your body's sleep-wake pattern.

adj. relating to or occurring approximately every twenty-four hours. Often describes biological rhythms that regulate sleep, metabolism, and other physiological processes.

Examples

“My circadian rhythm is out of sync after traveling across several time zones.”

“Shift workers often struggle with their health because their circadian rhythms are disrupted by working night shifts.”

“The study suggests that exposure to artificial light at night can significantly suppress melatonin production, thereby interfering with the body's natural circadian clock and leading to chronic sleep disorders.”

Examples

simple

“My circadian rhythm is out of sync after traveling across several time zones.”

contextual

“Shift workers often struggle with their health because their circadian rhythms are disrupted by working night shifts.”

complex

“The study suggests that exposure to artificial light at night can significantly suppress melatonin production, thereby interfering with the body's natural circadian clock and leading to chronic sleep disorders.”

Real-World Examples

“It helps control the body's sleep and wake cycle, also known as the circadian rhythm.”
ScienceDaily · 29 Aug 2026
“And jet lag is closely linked to what are called our circadian rhythms – the body's internal body clock.”
BBC News · 5 Aug 2026

Etymology

From the Latin circā (“about”) and diēs (“a day”) with the English suffix -an. Compare circannual.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Domain

Biology

This entry

Level
C1 · Advanced
Frequency
Occasional
Updated

Scan code

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English Reference