Your internal 24-hour clock that regulates sleep, hormones, digestion, and energy.
Circadian rhythm
Why it matters
Working with it (consistent sleep and light exposure) improves nearly every other health habit.
In practice
Getting morning daylight within an hour of waking helps anchor your rhythm.
Related terms
Sleep hygiene, Melatonin
Definitions in the Knowledge A–Z are general education, not medical advice. They do not diagnose or treat any condition. Speak to a qualified professional about anything specific to you.