noun
diurnal cycle
Technical term in biology and chronobiology for a roughly 24-hour cycle, often used in contexts like circadian rhythms.
日内周期は、生物の睡眠や体温調節に関係している。
The diurnal cycle is related to organisms' sleep and body temperature regulation.
概日リズム (circadian rhythm) is a more common term for the internal biological clock, while 日内周期 is a broader, more technical term for the daily cycle itself.
Compound of 日内 (にちない, 'within a day') and 周期 (しゅうき, 'cycle, period').