What is the process called when a solvent moves through a semipermeable membrane from a solution of lower concentration to one of higher concentration?

The process described in the question is known as osmosis. Osmosis specifically refers to the movement of water (the solvent) through a semipermeable membrane from an area where the concentration of solute is lower to an area where the concentration of solute is higher. This process is essential in biological systems, as it helps regulate the balance of fluids between different compartments in organisms.

In osmosis, the semipermeable membrane allows only the solvent (usually water) to pass through while preventing the larger solute molecules from crossing. This behavior is vital for maintaining cellular homeostasis and is a fundamental concept in both biology and chemistry.

In contrast, diffusion involves the movement of molecules from an area of higher concentration to one of lower concentration, which is not limited to semipermeable membranes, and is driven by the concentration gradient of the solute rather than the solvent. Filtration is a mechanical process that separates particles from a fluid using a barrier, and evaporation is a physical change where a liquid turns into vapor. Therefore, the correct identification of the process as osmosis aligns with its specific definition and role in various biological processes.