International Encyclopedia of Systems and Cybernetics

A pattern of movement, characterized by the recurrence at a regular frequency of some pulse in a process or system.

Rhythms are ebbs and rises in periodic phenomena.

They are generally a synchronic response (in phase or out of phase) to some other rhythm at a more embracing level. They can be simple or complex and are observable on the whole scale of phenomena, from nuclear physics to cosmic ones. They are also present in ecology, economy and in social evolution.

They should thus be considered as a general family of isomorphic features in systems.

Rhythms are present, for instance, in climates (and all biological and economic activities under their dependence: for ex. circadian rhythms), in oceanic tides, in light and sound and generally electromagnetic waves; in populations ecology; in physiological activities (from heartbeats to vegetal growth) and quite possibly in history.

C.A. BOGDANSKI has produced an interesting list of correspondences between physical or biochemical rhythms and physiological ones (1969, p.113).

There is a great variety of rhythms, corresponding to oscillations of short, medium and long periods or frequencies; and also to specific systemic and subsystemic processes.