Hypotonic Solution
A solution with a lower osmotic pressure than the one it is compared with, so water flows into the more concentrated side.
Formula / equation
π_solution < π_cell
Unit
atm
In depth
Cells in a hypotonic medium take in water and swell. Animal cells may burst, a process called haemolysis, while plant cells are restrained by their rigid cell walls and become turgid — which is precisely how plants stay upright.
Examples in the real world
Wilted lettuce becoming crisp in cold water; red blood cells lysing in distilled water.