Define tonicity and be able to use the terms isotonic, hypertonic and hypotonic

Tonicity is the concentration of solutes dissolved in a solution which determines the direction and extent of diffusion. Hypertonic is when the concentration of solutes is higher outside the cell than inside, so water flows in and the cell shrinks. Hypotonic is when concentration of solutes is higher inside cell than outside, water flows out and the cell bloats. Isotonic is equilibrium, water is flowing in and out.