What's the difference between diffusion and osmosis?

These 2 processes can be easily confused because they are both based on the idea of molecules moving from an area of HIGH concentration to LOW concentration. Diffusion= movement of ANY molecule. From an area of high concentration to low concentration. Osmosis: movement of WATER molecules. (ONLY water molecules) Down a conctration gradient (from high conc. to low conc.) Through a PARTIALLY PERMEABLE MEMBRANE. When answering an exam question on osmosis it is important to remember those 3 key points.