[oz-moh-sis, os-]
Physical Chemistry, cell Biology.
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.
the diffusion of fluids through membranes or porous partitions. Compare endosmosis, exosmosis.
a subtle or gradual absorption or mingling: He never studies but seems to learn by osmosis.

1865–70; Latinized form of now obsolete osmose osmosis, extracted from endosmose endosmosis, exosmose exosmosis < French, equivalent to end- end-, ex- ex-2 + Greek ōsm(ós) push, thrust + French -ose -osis

osmotic [oz-mot-ik, os-] , adjective
osmotically, adverb
nonosmotic, adjective
nonosmotically, adverb
unosmotic, adjective
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World English Dictionary
osmosis (ɒzˈməʊsɪs, ɒs-)
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
[C19: Latinized form from osmose (n), from Greek ōsmos push, thrust]

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Word Origin & History

1867, originally endosmose (1830s) "inward passage of a fluid through a porous septum," from Fr. endo- "inward" + Gk. osmos "a thrusting, a pushing," from othein "to push, to thrust," from PIE *wedhe- "to push, strike" (cf. Skt. vadhati "pushes, strikes, destroys," Avestan vadaya- "to repulse"). Fig.
sense is from 1900.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

osmosis os·mo·sis (ŏz-mō'sĭs, ŏs-)
n. pl. os·mo·ses (-sēz)

  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.

os·mot'ic (-mŏt'ĭk) adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
osmosis   (ŏz-mō'sĭs)  Pronunciation Key 

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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.
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Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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American Heritage
Cultural Dictionary
osmosis [(ahz-moh-sis, ahs-moh-sis)]

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.

Note: Informally, “osmosis” is the process by which information or concepts come to a person without conscious effort: “Living in Paris, he learned French slang by osmosis.”
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Example sentences
We are big bags full of all sorts of little bags, so getting all the osmotic pressures more or less correct is pretty important.
Osmotic fragility is a test to detect whether red blood cells are more likely to break down.
However, the membranes separating these subdivisions are permeable, and osmotic flow from one to another is the norm.
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