tonicity

Tonicity refers to how a solution surrounding a cell affects its water balance, based on the concentration of solutes (like salts or sugars) outside the cell compared to inside. If the outside solution has more solutes, water moves out of the cell, causing it to shrink (hypertonic). If there's less solute outside, water moves into the cell, making it swell (hypotonic). When the outside solution has an equal concentration of solutes as inside the cell, no net water movement occurs (isotonic). Tonicity influences cell shape and function by determining water movement across the cell membrane.