from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun The process of diffusing or the condition of being diffused.
  • noun The scattering of incident light by reflection from a rough surface.
  • noun The transmission of light through a translucent material.
  • noun The spontaneous intermingling of the particles of two or more substances as a result of random thermal motion.
  • noun The spread of linguistic or cultural practices or innovations within a community or from one community to another.

from The Century Dictionary.

  • noun In psychology, the law, formulated by A. Bain, that “according as an impression is accompanied with feeling, the aroused currents diffuse themselves freely over the brain, leading to a general agitation of the moving organs, as well as affecting the viscera.”
  • noun The act of diffusing, or the state of being diffused.
  • noun A scattering, dispersion, or dissemination, as of dust or seed, or of animals or plants.
  • noun Propagation or spread, as of knowledge or doctrine.
  • noun Diffuseness; prolixity.
  • noun Conduction of heat.
  • noun Synonyms Spread, circulation, expansion, dissemination, distribution.

from the GNU version of the Collaborative International Dictionary of English.

  • noun The act of diffusing, or the state of being diffused; a spreading; extension; dissemination; circulation; dispersion.
  • noun (Physiol.) The act of passing by osmosis through animal membranes, as in the distribution of poisons, gases, etc., through the body. Unlike absorption, diffusion may go on after death, that is, after the blood ceases to circulate.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun the act of diffusing or dispersing something, or the property of being diffused or dispersed; dispersion
  • noun physics the scattering of light by reflection from a rough surface, or by passage through a translucent medium
  • noun physics the intermingling of the molecules of a fluid due to random thermal agitation
  • noun the spread of cultural or linguistic practices, or social institutions, in one or more communities
  • noun physics, weather Exchange of airborne media between regions in space in an apparently random motion of a small scale.
  • noun the movement of water vapor from regions of high concentration (high water vapor pressure) toward regions of lower concentration.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun the spread of social institutions (and myths and skills) from one society to another
  • noun (physics) the process in which there is movement of a substance from an area of high concentration of that substance to an area of lower concentration
  • noun the property of being diffused or dispersed
  • noun the act of dispersing or diffusing something


from Wiktionary, Creative Commons Attribution/Share-Alike License

From Latin diffusionem (accusative of diffusio), from verb diffundere.


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  • The term diffusion applies both to dissemination of information about a new technology and dissemination of the technology itself; for instance, new cooking stoves.

    1. Rural common property resources: a growing crisis. 1992

  • I like to use reflected light as much as possible, and the source can be anything as long as the angle and diffusion is good.

    Sell A House With Creative Photo Lighting | Lifehacker Australia 2009

  • Random diffusion is a type of stochastic process, so if the theory of cosmogenic drift is to be developed, and if observable predictions are to be derived from it, then it will be necessary to employ the mathematics of stochastic processes.

    Archive 2009-01-01 Gordon McCabe 2009

  • The simplest type of diffusion is Brownian motion, (also termed a Wiener process), which is a simple random walk in which the increments between random variables St have a normal distribution with a mean value of zero.

    Archive 2009-01-01 Gordon McCabe 2009

  • An ID proponent, citing Dembski in No Free Lunch, insists that diffusion is not possible inside of living cells.

    College professor: "Flunk the IDiots" 2006

  • There is a need to anticipate technical characteristics - such as performance, cost, and diffusion - of new energy technologies such as photovoltaics, hydrogen production, and fuel cells; the long-term diffusion, transfer, and performance of these technologies depends on near-term RD&D and investment policies and decisions.

    Chapter 10 2000

  • The rate of diffusion is determined by the difference between the tension in the blood and that in the surrounding tissue.

    Physiology or Medicine 1920 - Presentation Speech 1967

  • We have direct evidence that only a small part of the acetylcholine so injected actually reaches the muscle end plates by diffusion from the vessels; and we argued that, in any case, it could not reach them simultaneously, but only in rapid succession; so that the response, in spite of its superficial resemblance to a rather slow twitch, must actually be

    Sir Henry Dale - Nobel Lecture 1965

  • Thus Jefferson's early, eloquent denunciations of slavery (whether sincere or half-hearted) gave way to cheerleading for what he called "diffusion" -- the proposition that, if slavery were expanded into the western territories, it would somehow dilute itself and go away, never mind the cost to its victims in the meantime.

    Bookmarks 2008

  • Considering the manner in which acetylcholine must reach the motor end plates of the muscle fibres, if it were indeed the transmitter of motor nerve excitation - that it must appear with a flash-like suddenness, in high concentration, simultaneously at every nerve ending - we concluded that the ordinary method of injecting acerylcholine, so that it reached the muscle by slow diffusion from the general circulation, could not possibly reproduce this abrupt appearance at the points responsive to its action.

    Sir Henry Dale - Nobel Lecture 1965


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  • (n): in cinematography, 1. a filter used on the camera to create a soft focus effect. 2. a white or pearlescent sheet of material used on a movie light to soften the shadows.

    January 18, 2009