1. Physical Chemistry, Cell Biology.
   1. the tendency of a fluid, usually water, to pass through a semipermeable membrane into a solution where the solvent concentration is higher, thus equalizing the concentrations of materials on either side of the membrane.
   2. the diffusion of fluids through membranes or porous partitions.Compare endosmosis, exosmosis.
2. a subtle or gradual absorption or mingling: He never studies but seems to learn by osmosis.

1. the passage of a solvent through a semipermeable membrane from a less concentrated to a more concentrated solution until both solutions are of the same concentration
2. diffusion through any membrane or porous barrier, as in dialysis
3. gradual or unconscious assimilation or adoption, as of ideas

1867, 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," from PIE *wedhe- "to push, strike" (cf. Sanskrit vadhati "pushes, strikes, destroys," Avestan vadaya- "to repulse"). Figurative sense is from 1900. Related: Osmotic (1854, from earlier endosmotic).

1. Diffusion of fluid through a semipermeable membrane until there is an equal concentration of fluid on both sides of the membrane.
2. The tendency of fluids to diffuse in such a manner.

1. The movement of a solvent through a membrane separating two solutions of different concentrations. The solvent from the side of weaker concentration usually moves to the side of the stronger concentration, diluting it, until the concentrations of the solutions are equal on both sides of the membrane.♦ The pressure exerted by the molecules of the solvent on the membrane they pass through is called osmotic pressure. Osmotic pressure is the energy driving osmosis and is important for living organisms because it allows water and nutrients dissolved in water to pass through cell membranes.

The seeping of a fluid through a seemingly solid barrier, such as a cell wall or a rubber sheet. When the concentration of the fluid is the same on both sides of the barrier, osmosis stops.