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Brownian motion Syllabification: Brown·i·an mo·tion
Pronunciation: /ˌbrounēən ˈmōSHən/

Definition of Brownian motion in English:


The erratic random movement of microscopic particles in a fluid, as a result of continuous bombardment from molecules of the surrounding medium.
Example sentences
  • Second, he explained the jittery dance of microscopic particles - Brownian motion - as the buffets of surrounding atoms.
  • The amplitude of the displacements of unattached beads diminishes with a constant slope of - 2, as expected for Brownian motion in a viscous medium (sugar water).
  • This does not occur in practice, since random forces such as Brownian motion perturb the cell's trajectory.


Late 19th century: named after Robert Brown (1773–1858), the Scottish botanist who first observed the motion.

Definition of Brownian motion in:
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