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[floo-res-uh ns, flaw-, floh-] /flʊˈrɛs əns, flɔ-, floʊ-/
noun, Physics, Chemistry.
the emission of radiation, especially of visible light, by a substance during exposure to external radiation, as light or x-rays.
Compare phosphorescence (def 1).
the property possessed by a substance capable of such emission.
the radiation so produced.
Origin of fluorescence
1852; fluor(spar) + -escence, on the model of opalescence, in reference to the mineral's newly discovered property
Related forms
nonfluorescence, noun
Can be confused
florescence, fluorescence. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for fluorescence
Historical Examples
  • Phosphorescence is exhibited chiefly by solids, fluorescence also by liquids and vapors.

    The Nature of Animal Light E. Newton Harvey
  • fluorescence is most efficiently excited by the cathode rays of a vacuum tube.

    The Nature of Animal Light E. Newton Harvey
  • We must conclude that animal light is not a fluorescence of any substance due to radiation produced by the animals themselves.

    The Nature of Animal Light E. Newton Harvey
  • A trace of alkali usually increases and acid inhibits the fluorescence of solutions.

    The Nature of Animal Light E. Newton Harvey
  • The ultraviolet rays falling upon this screen were transformed into visible rays by the phenomenon of fluorescence.

    Artificial Light M. Luckiesh
  • That is so, sir, and then we shall have the advantage of invisibility, and the enemy ships will be in fluorescence.

  • A study of riboflavin metabolism in the American roach by fluorescence microscopy.

  • Muscarine is isomeric with betain and oxycholin, from which it is separated by its fluorescence and poisonous properties.

    Poisons: Their Effects and Detection Alexander Wynter Blyth
  • The fluorescence from them streamed along our hull and down past the stern, like twin rocket tails.

    Wandl the Invader Raymond King Cummings
  • If the quantity is increased beyond something like the proportion stated, the fluorescence becomes less and very soon disappears.

    Soap-Bubbles C. V. Boys
British Dictionary definitions for fluorescence


  1. the emission of light or other radiation from atoms or molecules that are bombarded by particles, such as electrons, or by radiation from a separate source. The bombarding radiation produces excited atoms, molecules, or ions and these emit photons as they fall back to the ground state
  2. such an emission of photons that ceases as soon as the bombarding radiation is discontinued
  3. such an emission of photons for which the average lifetime of the excited atoms and molecules is less than about 10–8 seconds
the radiation emitted as a result of fluorescence Compare phosphorescence
Word Origin
C19: fluor + -escence (as in opalescence)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for fluorescence

1852, "glowing in ultraviolet light," coined by English mathematician and physicist Sir George G. Stokes (1819-1903) from fluorspar (see fluorine), because in it he first noticed the phenomenon, + -escence, on analogy of phosphorescence.

Online Etymology Dictionary, © 2010 Douglas Harper
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fluorescence in Medicine

fluorescence fluo·res·cence (flu-rěs'əns, flô-)

  1. The emission of electromagnetic radiation, especially of visible light, stimulated in a substance by the absorption of incident radiation and persisting only as long as the stimulating radiation is continued.

  2. The property of emitting such radiation.

fluo·res'cent 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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fluorescence in Science
  1. The giving off of light by a substance when it is exposed to electromagnetic radiation, such as visible light or x-rays. As long as electromagnetic radiation continues to bombard the substance, electrons in the fluorescent material become excited but return very quickly to lower energy, giving off light, always of the same frequency. Fluorescent dyes are often used in microscopic imaging, where different dyes can penetrate and illuminate different parts of the sample being examined, helping to distinguish its structures. Compare phosphorescence.

  2. The light produced in this way.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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fluorescence in Culture

fluorescence definition

The emission of light from an object as a result of bombardment by other kinds of electromagnetic radiation, such as x-rays or ultraviolet rays. Fluorescent materials may appear one color when bathed in visible light and another color when exposed to other kinds of electromagnetic radiation.

Note: “Black light” depends on fluorescence for its effects.
The 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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