Osmosis is the movement of molecules from a region of lower concentration to a region of higher concentration through a semi-permeable membrane
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Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration until the molecules are evenly distributed
<em>In diffusion, particles move from an area of higher concentration to one of lower concentration until equilibrium is reached. In osmosis, a semipermeable membrane is present, so only the solvent molecules are free to move to equalize concentration.</em>