[ floo-res-uhns, flaw-, floh- ]
See synonyms for fluorescence on Thesaurus.com
nounPhysics, Chemistry.
  1. 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).

  2. the property possessed by a substance capable of such emission.

  1. 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

Other words from fluorescence

  • non·fluo·res·cence, noun

Words that may be confused with fluorescence

Words Nearby fluorescence

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use fluorescence in a sentence

British Dictionary definitions for fluorescence


/ (ˌflʊəˈrɛsəns) /

  1. physics

    • 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

    • such an emission of photons that ceases as soon as the bombarding radiation is discontinued

    • such an emission of photons for which the average lifetime of the excited atoms and molecules is less than about 10 –8 seconds

  2. the radiation emitted as a result of fluorescence: Compare phosphorescence

Origin of fluorescence

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

Scientific definitions for fluorescence


[ flu-rĕsəns ]

  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 © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for fluorescence


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.

Notes for fluorescence

“Black light” depends on fluorescence for its effects.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.