[link to en.wikipedia.org]

In common usage, "chaos" means "a state of disorder".

[7] However, in chaos theory, the term is defined more precisely. Although there is no universally accepted mathematical definition of chaos, a commonly used definition says that, for a dynamical system to be classified as chaotic, it must have the following properties:[8]

it must be sensitive to initial conditions;
it must be topologically mixing; and
its periodic orbits must be dense.

The requirement for sensitive dependence on initial conditions implies that there is a set of initial conditions of positive measure which do not converge to a cycle of any length.