The word "stochastic" means "pertaining to chance" (Greek roots), and is thus used to describe subjects that contain some element of random or stochastic behavior. For a system to be stochastic, one or more parts of the system has randomness associated with it. Unlike a deterministic system, for example, a stochastic system does not always produce the same output for a given input. A few components of systems that can be stochastic in nature include stochastic inputs, random time-delays, noisy (modelled as random) disturbances, and even stochastic dynamic processes.