The term that describes the concentration of solutes in a solution is called osmolarity. Osmolarity measures the total number of solute particles in a unit volume of solution, influencing water movement across membranes through the process of osmosis. It is crucial in biological contexts, as cells must maintain specific osmolarity levels to function properly. Disturbances in osmolarity can lead to cellular dysfunction, impacting processes like hydration, nutrient absorption, and overall homeostasis within organisms.