# circadian

/sɝˈkeɪdiən/ (US) · /sɜːkˈeɪdiən/ (UK) · CEFR C1 · Adjective

Source: https://englishreference.com/word/circadian
Updated: 2026-05-18

## Definition

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

For teachers: 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.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.