What is the definition of osmosis?

Osmosis is specifically defined as the movement of water molecules across a semi-permeable membrane. This process occurs when water moves from an area of lower solute concentration to an area of higher solute concentration, aiming to equalize solute concentrations on both sides of the membrane. This movement is passive, meaning it does not require energy, and is driven by the concentration gradient of water.

The emphasis on a semi-permeable membrane in the definition is crucial, as it allows water to pass through while potentially restricting other solutes from doing so. This characteristic differentiates osmosis from other processes such as diffusion or active transport, which may involve solute movement or require energy input, respectively. Understanding this concept is fundamental in cellular biology, where osmosis plays a key role in maintaining cell turgor and homeostasis.