Diffusion may refer to: In the physical sciences: Molecular diffusion (also commonly without additional attributes) - spontaneous dispersion of mass (distinct from migration, caused by an external force) Diffusion of heat Diffusion of momentum Diffusion equation - a mathematical formalism describing the spreading of a conserved property caused by its own density gradient Heat equation Eddy diffusion In physical sciences, more specific or modified meanings: Acoustic diffusion of sound wa… (More on Diffuse)