"The movement of chemical species (ions or molecules ) under the influence of concentration difference. The species will move from the high concentration area to the low concentration area till the concentration is uniform in the whole phase. Diffusion in solutions is the most important phenomenon in electrochemistry, but diffusion will occur also in gases and solids. The rate of diffusion (diffusional flux) is proportional to the gradient of the concentration in the solution, with the proportionality constant called the ""diffusion coefficient."" "
Meaning of DIFFUSION in English
Electrochemistry English dictionary. Английский словарь электрохимии. 2012