Meaning of Graham's law of diffusion

Gra'ham's law' of diffu'sion

Pronunciation: [key]
— Physical Chem. Physical Chem.
  1. the principle that at a given temperature and pressure the rate of diffusion of a gas is inversely proportional to the square root of its density.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.