**[Terminology] Brownian motion**

**Definition:**the random motion that the particles suspending in liquid conduct.

In 1827, Britain botanist Brown first discovered, so called Brownian motion.

Brownian motion is a typical fractal.

Theory of molecular motion can make correct and reasonable interpretations of Brownian motion.

Molecules of liquid are always in motion, the fine particles suspending in the liquid are always in force imbalance, the fine particles move inevitably, and directions of movements are random.

However, the particles always move from higher concentration to lower concentration, this is diffusion phenomena.

Obviously, diffusion is macroscopic manifestation of Brownian motion; Brownian motion is micro-foundation of diffusion.

In 1905, Einstein proposed Brownian motion equation:

In the equation:

: average displacement; R: gas constant; T: temperature; N

_{A}: Avogadro constant; t: displacement time; η: medium viscosity; r: particle diameter.According to Einstein's Brownian motion equation, may calculate Avogadro constant.