+The **circadian clock** is an internal, roughly 24-hour rhythm that regulates many biological processes. These [Biological Rhythms](/wiki/biological_rhythms) influence sleep-wake cycles, hormone release, and [Metabolism](/wiki/metabolism), adapting organisms to the Earth's light-dark cycle.
+## See also
+- [Sleep](/wiki/sleep)
+- [Melatonin](/wiki/melatonin)
+- [Chronobiology](/wiki/chronobiology)
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