Diffusion of water across a selectively permeable membrane is a process known as osmosis. A selectively permeable membrane allows certain molecules or ions to pass through while blocking others. In the case of osmosis, the membrane permits water molecules to move but may restrict the passage of solutes (such as salts or other substances).
During osmosis, water moves from an area of lower solute concentration (where there is a higher concentration of water molecules) to an area of higher solute concentration (where there is a lower concentration of water molecules). This movement continues until there is an equilibrium reached, meaning the solute concentrations on either side of the membrane become equal.
Osmosis is a crucial process in biological systems, as it helps regulate the internal environment of cells, maintains cell shape, and is involved in various physiological processes such as nutrient absorption and waste removal.