[spek-truh m]
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noun, plural spec·tra [spek-truh] /ˈspɛk trə/, spec·trums.
  1. Physics.
    1. an array of entities, as light waves or particles, ordered in accordance with the magnitudes of a common physical property, as wavelength or mass: often the band of colors produced when sunlight is passed through a prism, comprising red, orange, yellow, green, blue, indigo, and violet.
    2. this band or series of colors together with extensions at the ends that are not visible to the eye, but that can be studied by means of photography, heat effects, etc., and that are produced by the dispersion of radiant energy other than ordinary light rays.Compare band spectrum, electromagnetic spectrum, mass spectrum.
  2. a broad range of varied but related ideas or objects, the individual features of which tend to overlap so as to form a continuous series or sequence: the spectrum of political beliefs.

Origin of spectrum

1605–15; < Latin: appearance, form, equivalent to spec(ere) to look, regard + -trum instrumental noun suffix
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for spectrum


noun plural -tra (-trə)
  1. the distribution of colours produced when white light is dispersed by a prism or diffraction grating. There is a continuous change in wavelength from red, the longest wavelength, to violet, the shortest. Seven colours are usually distinguished: violet, indigo, blue, green, yellow, orange, and red
  2. the whole range of electromagnetic radiation with respect to its wavelength or frequency
  3. any particular distribution of electromagnetic radiation often showing lines or bands characteristic of the substance emitting the radiation or absorbing itSee also absorption spectrum, emission spectrum
  4. any similar distribution or record of the energies, velocities, masses, etc, of atoms, ions, electrons, etca mass spectrum
  5. any range or scale, as of capabilities, emotions, or moods
  6. another name for an afterimage

Word Origin for spectrum

C17: from Latin: appearance, image, from spectāre to observe, from specere to look at
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

Word Origin and History for spectrum

1610s, "apparition, specter," from Latin spectrum "appearance, image, apparition," from specere "to look at, view" (see scope (n.1)). Meaning "band of colors formed from a beam of light" first recorded 1670s.

Online Etymology Dictionary, © 2010 Douglas Harper

spectrum in Medicine


n. pl. spec•trums
  1. The distribution of a characteristic of a physical system or phenomenon, especially the distribution of energy emitted by a radiant source arranged in order of wavelengths.
  2. The color image presented when white light is resolved into its constituent colors: red, orange, yellow, green, blue, indigo, violet.
  3. The plot of intensity as opposed to wavelength of light emitted or absorbed by a substance, usually characteristic of the substance and used in qualitative and quantitative analysis.
  4. The distribution of atomic or subatomic particles in a system, as in a magnetically resolved molecular beam, arranged in order of masses.
  5. The group of pathogenic organisms against which an antibiotic or other antibacterial agent is effective.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

spectrum in Science


Plural spectra (spĕktrə) spectrums
  1. A range over which some measurable property of a physical phenomenon, such as the frequency of sound or electromagnetic radiation, or the mass of specific kinds of particles, can vary. For example, the spectrum of visible light is the range of electromagnetic radiation with frequencies between between 4.7 X 1014 and 7.5 X 1014 hertz.
  2. The observed distribution of a phenomenon across a range of measurement. See more at atomic spectrum spectroscopy.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

spectrum in Culture


The range of wavelengths characteristic of a specific type of radiation.


The spectrum making up visible light contains light in the colors violet, indigo, blue, green, yellow, orange, and red, with violet having the shortest wavelength and highest frequency, and red having the longest wavelength and lowest frequency.
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.