The term "circadian" refers to biological processes that follow a roughly 24-hour cycle. These rhythms are influenced by external factors like light and temperature, helping organisms adapt to the day-night cycle. Circadian rhythms regulate various functions, including sleep-wake cycles, hormone release, and metabolism. In humans, the circadian rhythm is primarily controlled by the suprachiasmatic nucleus, a group of cells in the brain that responds to light signals. Disruptions to this rhythm, such as shift work or irregular sleep patterns, can lead to health issues like sleep disorders and decreased cognitive function.