Chaos and instability.

A common misunderstanding is to think that chaos and instability are the same thing. The two concepts may indeed be closely related sometimes, but are not equivalent.

Chaos and instability, concepts only beginning to acquire formal definitions, were not the same at all. A chaotic system could be stable if its particular brand of irregularity persisted in the face of small disturbances. (...) The chaos Lorenz discovered, with all its unpredictability, was as stable as a marble in a bowl. You could add noise to this system, jiggle it, stir it up, interfere with its motion, and then when everything settled down, the transients dying away like echoes in a canyon, the system would return to the same peculiar pattern of irregularity as before. It was locally unpredictable, globally stable. Real dynamical systems played by a more complicated set of rules than anyone had imagined.

(Gleick: pp. 48-49).

To a certain extent, we can use free market as an example. As a system, it's definitely chaotic but far from unstable. Sure, there are ups and downs (the infamous economic cycle) but one can hardly call a cycle unstable. After all, one of its most prominent characteristics is that it repeats itself.