The process of net diffusion of water molecules from a dilute solution or pure water to a more concentrated solution when both are seperated by a semipermeable membrane.there is a pressure which has to be exerted on the concentrated solution,seperated from pure water by a semipermeable membrane.Osmotic pressureof a dilute solution is directly propotional to other colligative properties like the fall in freezing point, lowering of vapour pressure,etc. Osmotic pressure inversely propotinal to the MW of the solute.
