AskDefine | Define spectrum

Dictionary Definition



1 an ordered array of the components of an emission or wave
2 broad range of related values or qualities or ideas or activities [also: spectra (pl)]

User Contributed Dictionary



  • /ˈspektrəm/
  • a unknown /ˈspɛktrəm/, /"spEktr@m/


  1. A range; a continuous, infinite, one-dimensional set, possibly bounded by extremes.
  2. Specifically, a range of colours representing light (electromagnetic radiation) of contiguous frequencies; hence electromagnetic spectrum, visible spectrum, ultraviolet spectrum, etc.
  3. The pattern of absorption or emission of radiation produced by a substance when subjected to energy (radiation, heat, electricity, etc.).
  4. Of a bounded linear operator A, the scalar values λ such that the operator A—λI, where I denotes the identity operator, does not have a bounded inverse.

Derived terms


  • Italian: spettro
  • Japanese: スペクトル
  • Romanian: spectru
  • Russian: спектр, диапазон
range of colors
  • Czech: spektrum
  • Hebrew: ספקטרום
  • Italian: spettro
  • Japanese: スペクトル, 分光特性
  • Romanian: spectru
  • Russian: спектр
chemistry: a pattern of absorption or emission of radiation
  • Japanese: スペクトル
linear algebra: set of scalar values
  • Italian: spettro
  • Japanese: スペクトル
  • Romanian: spectru
  • Russian: спектр



  1. a specter

Related terms

Extensive Definition

A spectrum (plural spectra or spectrums) is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by analogy to many fields. Thus one might talk about the spectrum of political opinion, or the spectrum of activity of a drug, or the autism spectrum. In these uses, values within a spectrum are not necessarily precisely defined numbers as in optics; exact values within the spectrum are not precisely quantifiable. Such use implies a broad range of conditions or behaviors grouped together and studied under a single title for ease of discussion.
In most modern usages of spectrum there is a unifying theme between extremes at either end. Some older usages of the word did not have a unifying theme, but they led to modern ones through a sequence of events set out below. Modern usages in mathematics did evolve from a unifying theme, but this may be difficult to recognize.


In Latin spectrum means "image" or "apparition", including the meaning "spectre". Spectral evidence is testimony about what was done by spectres of persons not present physically, or hearsay evidence about what ghosts or apparitions of Satan said. It was used to convict a number of persons of witchcraft at Salem, Massachusetts in the late 17th century.

Modern meaning in the physical sciences

In the 17th century the word spectrum was introduced into optics, referring to the range of colors observed when white light was dispersed through a prism. Soon the term referred to a plot of light intensity or power as a function of frequency or wavelength, also known as a spectral density.
The term spectrum was soon applied to other waves, such as sound waves, and now applies to any signal that can be decomposed into frequency components. A spectrum is a usually 2-dimensional plot, of a compound signal, depicting the components by another measure. Sometimes, the word spectrum refers to the compound signal itself, such as the "spectrum of visible light", a reference to those electromagnetic waves which are visible to the human eye. Looking at light through a prism separates visible light into its colors according to wavelength. It separates them according to its dispersion relation and a grating separates according to the grating equation and if massive particles are measured often their speed is measured. To get a spectrum, the measured function has to be transformed in their independent variable to frequencies and the dependent variable has to be reduced in regions, where the independent variable is stretched. For this imagine that the spectrum of pulse with a finite number of particles is measured on a film or a CCD. Assuming no particles are lost, any nonlinearity (compared to frequency) on the spectral separation concentrates particles at some points of the film. The same is true for taking a spectrum by scanning a monochromator with a fixed slit width. Violet at one end has the shortest wavelength and red at the other end has the longest wavelength of visible light. The colors in order are violet, blue, green, yellow, orange, red. As the wavelengths get bigger below the red visible light they become infrared, microwave, and radio. As the wavelengths get smaller above violet light, they become ultra-violet, x-ray, and gamma ray.
spectrum in Bosnian: Spektar (fizika)
spectrum in Catalan: Espectre
spectrum in Persian: طیف
spectrum in Korean: 스펙트럼
spectrum in Ido: Spektro
spectrum in Indonesian: Spektrum
spectrum in Italian: Spettro (astronomia)
spectrum in Hebrew: ספקטרום
spectrum in Dutch: Spectrum
spectrum in Japanese: スペクトル
spectrum in Norwegian: Spekter
spectrum in Polish: Widmo (spektroskopia)
spectrum in Portuguese: Espectro (física)
spectrum in Russian: Спектр
spectrum in Simple English: Spectrum
spectrum in Slovenian: Spekter
spectrum in Serbian: Спектар (физичка хемија)
spectrum in Finnish: Spektri
spectrum in Swedish: Spektrum
spectrum in Thai: สเปกตรัม
spectrum in Ukrainian: Спектр
spectrum in Chinese: 光學頻譜

Synonyms, Antonyms and Related Words

AF, CPS, Dalmatian, EHF, HF, Hz, Indian file, MF, Maxwell triangle, Munsell scale, RF, SHF, UHF, VHF, VLF, afterimage, antigorite, array, articulation, audio frequency, bank, bogey, butterfly, buzz, candy cane, carrier frequency, carry, catena, catenation, chain, chain reaction, chaining, chameleon, cheetah, chromatic circle, chromatic spectrum, chromaticity diagram, chrysotile, color circle, color cycle, color index, color mixture curve, color solid, color spectrum, color system, color triangle, compass, complementary color, concatenation, confetti, connection, consecution, continuum, course, crazy quilt, cycle, cycles, demitint, descent, diapason, drone, eidolon, endless belt, endless round, extremely high frequency, file, filiation, firedog, frequency, frequency spectrum, full color, fundamental colors, gamut, ghost, gradation, half tint, halftone, harlequin, haunt, hertz, high frequency, hue cycle, hum, intermediate frequency, iris, jaguar, kilocycles, kilohertz, leopard, line, lineage, low frequency, lower frequencies, mackerel, mackerel sky, marble, marbled paper, medium frequency, megacycles, megahertz, metamer, moire, monochrome, monotone, mother-of-pearl, nacre, nexus, ocelot, ocular spectrum, opal, ophite, optical illusion, patchwork quilt, peacock, pendulum, periodicity, phantasm, plenum, powder train, primary, primary color, progression, pure color, queue, radio frequency, radius, rainbow, range, rank, reach, recurrence, register, reticulation, revenant, rotation, round, routine, row, run, scale, scope, secondary, secondary color, sequence, series, serpentine, serpentine marble, shade, shot silk, single file, solar spectrum, spark frequency, spectral color, spectrum color, spirit, spook, stretch, string, succession, superhigh frequency, swath, sweep, tertiary, tertiary color, thread, tier, tortoise shell, train, trick of eyesight, ultrahigh frequency, upper frequencies, very high frequency, very low frequency, windrow, zebra
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