An isotonic solution is a type of solution that has the same concentration of solutes as another solution, typically a cell's internal environment. This balance allows for the equal movement of water in and out of the cell, preventing any net gain or loss of water. Isotonic solutions are crucial in biological systems, as they help maintain cell shape and function. In medical settings, isotonic solutions, such as saline or lactated Ringer's solution, are often used for intravenous (IV) therapy. These solutions help to rehydrate patients without causing cells to swell or shrink, ensuring that bodily functions remain stable during treatment.