||This article needs attention from an expert in Physics. (January 2009)
Predictability is the degree to which a correct prediction or forecast of a system's state can be made either qualitatively or quantitatively.
Predictability in Statistical Physics
Although the second law of thermodynamics can tell us about the equilibrium state that a system will evolve to, and steady states in dissipative systems can sometimes be predicted, there exists no genum, e.g. chaotic systems, if they do not approach an equilibrium state. Their predictability usually deteriorates with time and to quantify predictability, the rate of divergence of system trajectories in phase space can be measured (Kolmogorov-Sinai entropy, Lyapunov exponents).
Predictability in Mathematics
In stochastic analysis a random process is a predictable process if it is possible to know the "next" state at the present time.
Predictability in Human–computer interaction
In the study of human–computer interaction, predictability is the property to forecast the consequences of a user action given the current state of the system.