Final answer:
A hypertonic solution has a higher osmolarity than a cell's cytoplasm, leading to water exiting the cell, known as crenation in red blood cells and plasmolysis in plant cells.
Step-by-step explanation:
A hypertonic solution is one where the extracellular fluid has a higher osmolarity than the cytoplasm of a cell, causing water to move out of the cell. In such a solution, cells will lose water and shrink, which can be observed in red blood cells as crenation. Additionally, in plant cells, this phenomenon can result in the cell membrane detaching from the cell wall, known as plasmolysis.