The capacity of a system (particularly a living one) to accomodate its behavior to a great variety of situations.
N. RASHEVSKY observes: "A very important characteristic of an organismic set is that, while its elements can potentially exhibit a number of activities necessary for the preservation of (its) elements and of the set, in general only a subset of the set of all potentially possible activities is exhibited" (1967, p.22).
RASHEVSKY shows by a biological example that many possible adaptations remain latent if not needed, i.e. become actualized only if some environmental stimulus awakens them.
Consequently: "The wider the range of potentially possible activities of an element of an organismic set, the greater is the variety of environments in which this organismic set can survive" (Ibid)
This is in accordance with ASHBY's concept that only (internal) variety can destroy external variety.
It is also obvious that, in many organisms, if not in all of them, the full range of adaptability is never revealed.
On the other hand, as expressed by RASHEVSKY: "The adaptability may be very great but it is always limited. No set of genes, no multicellular organism, and no society can survive in every conceivable environment" (Ibid).
In any case, as observed by E. LASZLO, systems of high complexity trade stability for richness in adaptability (1972).