I can discover no technical word meaning a pathway of change which is equilibrated in the sense that the system tends to return to it after disturbance. One would have expected that such a notion was a commonplace of the kinetics or cybernetics of polyphasic systems. I should suggest that a reasonably short and suitable word would be ‘creode’, from the two Greek roots χρη, it is necessary, and ὁδος, a route or path. A creode, then, is a representation (e.g. by a trajectory in phase space) of a temporal succession of states of a system characterised by the property that the system, if constrained to move slightly away from the croede, will tend to return to it. The path followed by a homing missile, which finds its way to a stationary target, is a creode.