Osmosis is the passage of water from a weak solution to a strong solution through a semi permeable membrane.

A semi-permeable membrane is otherwise known as a selectively permeable membrane. It is a type of barrier that will allow the passage of some molecules but not others. In osmosis, water passes from one side of this membrane to the other. The water will move only in one direction--it will move from the side where the water is in highest concentration to the other side of the membrane. The liquid that the water moves into is a strong solution, so the water is acting to dilute the solution. If one side of the membrane has a solution of sugar and the other side has water then the water will flow into the sugar solution, diluting it. The pore size of the membrane is such that water molecules can readily...