Hypertonic refers to a solution that has a higher concentration of solutes compared to another solution, typically a cell's cytoplasm. When cells are placed in a hypertonic solution, water moves out of the cells through osmosis, leading to cell shrinkage or crenation. This concept is often important in Biology and medicine, particularly in understanding how cells interact with their environment. Hypertonicity can affect various physiological processes and is relevant in treatments involving intravenous fluids.