An equation in nonequilibrium statistical mechanics that describes a superposition of a dynamic friction (slowing-down) process and a diffusion process for the evolution of variables in a system. The Fokker–Planck equation, which can be used to analyse such problems as Brownian movement, is soluble using statistical methods and the theory of probability. It is named after the Dutch physicist Adriaan Fokker (1887–1968), who proposed it in 1914, and Max Planck, who discussed it in 1917.