What process describes the movement of water across a membrane?

The movement of water across a membrane is specifically referred to as osmosis. This process involves the diffusion of water molecules from an area of low solute concentration to an area of high solute concentration through a selectively permeable membrane. Osmosis is crucial in maintaining cellular homeostasis, as it regulates the internal environment of cells and tissues based on the osmotic gradient.

In this context, osmosis is distinct because it specifically pertains to water movement, whereas other processes like diffusion refer to the movement of solutes in general. Facilitated diffusion involves transporter proteins assisting in the movement of solutes across a membrane but does not specifically pertain to water. Active transport, on the other hand, requires energy to move substances against their concentration gradient and typically does not apply to the passive movement of water. Thus, osmosis is the correct term for the movement of water across a membrane.