Definition: The tendency of a phenomenon to recur at regular intervals; in biological systems, the recurrence of certain activities (including hormonal, cellular, neural) may be annual, seasonal, monthly, daily, or more frequently (ultradian).
IM + coord with specific dis for periodically occurring dis (IM); no qualif; do not confuse with PERIODIC DISEASE, a specific clin entity: see Dorland
See AlsoBiological Clocks; Circadian Rhythm ExamplesSeasons