Osmosis and diffusion are similar in that they are both processes of passive transport of solutes and water across a selectively permeable membrane. However, there are some important differences between the two processes: Direction of transport: Osmosis refers specifically to the movement of water molecules from an area of high concentration to an area of low concentration across a selectively permeable membrane. Diffusion refers to the movement of any solute, not just water, from an area of high concentration to an area of low concentration across a selectively permeable membrane. Driving force: The driving force behind osmosis is the difference in concentration of water molecules on either side of a selectively permeable membrane. The driving force behind diffusion is the difference in concentration of any solute on either side of a selectively permeable membrane. Membrane permeability: In osmosis, only water molecules are able to pass through a selectively permeable membrane. In diffusion, any solute can pass through a selectively permeable membrane, depending on its size and the permeability of the membrane. Overall, osmosis and diffusion are related processes that are involved in the movement of solutes and water across biological membranes. However, they differ in the direction of transport, the driving force behind the movement, and the types of molecules that can pass through the membrane.