[ spek-truhm ]
/ ˈspɛk trəm /
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See synonyms for: spectrum / spectra on Thesaurus.com

noun, plural spec·tra [spek-truh], /ˈspɛk trə/, spec·trums.
  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.
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.
the range of traits and behaviors that are considered to be characteristic of autism spectrum disorder.
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Idioms about spectrum

    on the spectrum, having an autism spectrum disorder, or displaying behaviors considered characteristic of those disorders: The nonprofit works to increase public awareness about the day-to-day issues faced by people on the spectrum.

Origin of spectrum

First recorded in 1605–15; from Latin: “appearance, form,” equivalent to spec(ere) “to look at, regard” + -trum instrumental noun suffix
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use spectrum in a sentence

British Dictionary definitions for spectrum

/ (ˈspɛktrəm) /

noun plural -tra (-trə)
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
the whole range of electromagnetic radiation with respect to its wavelength or frequency
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
any similar distribution or record of the energies, velocities, masses, etc, of atoms, ions, electrons, etca mass spectrum
any range or scale, as of capabilities, emotions, or moods
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

Scientific definitions for spectrum

[ spĕktrəm ]

Plural spectra (spĕktrə) spectrums
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.
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.

Cultural definitions for spectrum


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

notes for spectrum

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.