. . "A circadian rhythm /s\u025Cr\u02C8ke\u026Adi\u0259n/ is any biological process that displays an endogenous, entrainable oscillation of about 24 hours. These 24-hour rhythms are driven by a circadian clock, and they have been widely observed in plants, animals, fungi, and cyanobacteria.The term circadian comes from the Latin circa, meaning \"around\" (or \"approximately\"), and di\u0113s, meaning \"day\"."@en .