Osmotic pressure is the pressure
which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane.
It is also defined as the minimum pressure needed to nullify osmosis.The phenomenon of osmotic pressure arises from the tendency of a pure
solvent to move through a semi-permeable membrane and into a solution
containing a solute to which the membrane is impermeable.This process is of vital importance in biology as the cell's membrane is selective toward many of the solutes found in living organisms.