Instead of looking at the variation of velocity over time, as in the Wiener equation, the *Langevin equation* deals with the temporal change in acceleration due to a stochastic force:

- ,

If the stochastic force is zero, the system is deterministic, otherwise solutions can be obtained either by the Monte Carlo Method, i.e. simulating a statistical ensemble with different forcings and averaging, and statistically with the Fokker-Planck equation, which computes the change of probability density over time.