Diffusion may refer to: Diffusion, the spontaneous spreading of something such as particles, heat, light, or momentum In the physical sciences: Acoustic diffusion of sound waves Atomic diffusion Collective diffusion, the diffusion of a large number of (possibly interacting) particles Effusion of a gas through small holes Electron diffusion, producing electric current Thermal diffusion, in the form of Heat flow Knudsen diffusion of particles from very small containers Momentum diffusion… (More on Diffuse)