circadian
/sɜːˈkeɪdɪən/adjective
- Physiology (of biological processes) recurring naturally on a twenty-four-hour cycle, even in the absence of light fluctuations【生理】（生物作用）昼夜的：
a circadian rhythm.
生理节奏。
词源
1950s: formed irregularly from Latin circa 'about' + dies 'day'.