Why osmosis is regarded as a special diffusion?

Osmosis is regarded as a special case of diffusion because it describes the net movement of water molecules across a selectively permeable membrane. Like diffusion, osmosis is a passive process driven by a difference in concentration, moving from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration). The "special" aspect comes from the requirement of a selectively permeable membrane, which allows water to pass through but restricts the movement of solute particles.