### diffusion

(the spreading of particles toward an even distribution)

**Diffusion** is the net movement of particles such as atoms or
molecules from areas of higher concentration to areas of lower
concentration.

A **diffusion equation** is an equation describing diffusion
over time. **Fick's laws** include a diffusion equation describing
what happens in many cases, a type of diffusion termed
**Fickian diffusion**. The equation:

dC
J = -D ——
dx

- J - the
**diffusive flux**, the flow of the diffusing substance as substance/time.
- D - the
**diffusion coefficient** (i.e., **diffusivity**) of the substance.
- C - the concentration of the substance.
- x - measurement over a direction over which we are describing the diffusion.

(*physics,chemistry*)
http://en.wikipedia.org/wiki/Diffusion

http://mathbench.umd.edu/modules/cell-processes_diffusion/page09.htm

**Referenced by:**

atmospheric escape

stellar evolution

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