characteristic periodic change in a living organism or life-related process
EXAMPLE The circadian rhythm has a period of approximately 24 h.
Note 1 to entry: Biological rhythms can be influenced by optical radiation.
Note 2 to entry: This entry was numbered 845-06-26 in IEC 60050-845:1987.
Note 3 to entry: This entry was numbered 17-89 in CIE S 017:2011.