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/äzˈmōsis/  /äs-/


1. The spontaneous net movement of solvent molecules through a partially permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides. (

2. A physical process in which any solvent moves, without input of energy, across a semipermeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations. Although osmosis does not require input of energy, it does use kinetic energy and can be made to do work. (

3. The net movement of solvent molecules from a region of high solvent potential to a region of lower solvent potential through a partially permeable membrane. (

4. Tendency of water to flow from a hypotonic solution (low concentration of dissolved substances) to hypertonic solution (higher concentration of dissolved substances) across a semipermeable membrane. (

Word origin: Latinized from osmose (1854), shortened from endosmosis (1830s), from endosmose “inward passage of a fluid through a porous septum” (1829), from French endo– “inward” + Greek osmos “a thrusting, a pushing,” from stem of othein “to push, to thrust.”

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