Osmosis is a special type of diffusion. It is the scattering of only solvent molecules while there is scattering of both solute and solvent in diffusion to maintain concentration difference. Osmosis requires semi-permeable membrane but diffusion does not require any membrane or medium to happen. In osmosis, water or solvent moves from high water potential to low water potential while movement of solute and solvent occurs from high concentrate region to low concentrate region in diffusion.
