Osmosis is the diffusion of water from an area of lower solute concentration to an area of higher solute concentration through a semipermeable membrane. Because there is a higher concentration of solutes or other particles on the higher concentration side of the semipermeable membrane, there is a greater number of particles colliding with water molecules to inhibit their passage through the membrane compared to the side with lower concentration. Therefore, there is a net transfer of water molecules to equalize the solute concentration on both sides.