Diffusion

Acoustics

The scattering or random reflection of a sound wave from a surface. The directions of reflected sound is changed so that listeners may have sensation of sound coming from oil directions at equal levels.

Chemistry

The mixing of two substances caused by random molecular motions. Gases diffuse very quickly; liquids diffuse much more slowly, and solids diffuse at very slow, sometimes measurable, rates. Molecular collisions make diffusion slower in liquids and solids.

See also: Diffusion Coefficient, Diffusion Rate, Ficks Laws.