circadian

American  

[sur-key-dee-uhn] / sɜrˈkeɪ di ən /

adjective

Physiology.

1. of or relating to a biorhythm or regular biological cycle occurring once every 24 hours, such as waking and sleeping.

   Exposure to blue light at night can disrupt your circadian rhythm, making your biological clock think it's earlier in the day rather than time for bed.

   He is doing research related to the circadian cycling of hormones.

---

circadian British  

/ sɜːˈkeɪdɪən /

adjective

1. of or relating to biological processes that occur regularly at about 24-hour intervals, even in the absence of periodicity in the environment See also biological clock

---

Etymology

Origin of circadian

First recorded in 1955–60; from circā “about” + Latin di(ēs) “day” + -an ( def. ); circa ( def. )

Example Sentences

D.V.M.; a research fellow in the division of sleep and circadian disorders at Brigham and Women's Hospital and Harvard Medical School, both in Boston.

From Science Daily

He earned his PhD in 2006 from the Graduate School of Science at Nagoya University, where he studied the circadian clock in cyanobacteria.

From Science Daily

Biological sleep rhythms, known as circadian rhythms, naturally change during adolescence.

From Science Daily

Research published on December 29, 2025, in Neurology, the medical journal of the American Academy of Neurology, found that people with weaker and more irregular circadian rhythms were more likely to develop dementia.

From Science Daily

While metabolic measures remained largely unchanged, the timing of meals did affect circadian rhythms.

From Science Daily

Related Words

• constantly
• day-to-day
• everyday
• often
• periodic
• regular
• regularly
• routine