The word spectrum (plural, spectra) has many uses:

Common nouns

• The Spectrum article explains why so many things are called by this name
• The spectrum of activity of a drug
• The political spectrum of opinion
• The economic spectrum
• The bipolar spectrum, in psychology
• The autistic spectrum, in psychology

In most modern usages of the word spectrum, there is a unifying theme of a variety of possible cases between extremes at either end. ... The spectrum of activity of a drug is the range of diseases which it can treat. ... A political spectrum is a way of comparing or visualizing different political positions, by placing them upon one or more geometric axes. ... This article needs to be cleaned up to conform to a higher standard of quality. ... The bipolar spectrum is the continuous range of depressive diseases, ranging from bipolar disorder to unipolar depression. ... The autistic spectrum, or autism spectrum, is the idea that autism is a developmental and behavioral syndrome that results from certain combinations of traits. ...

In the physical sciences

• The energy spectrum of a collection of particles
• The electromagnetic spectrum, or an electromagnetic spectrum of an object
  • The optical spectrum or color spectrum, a subset of the electromagnetic spectrum
• An emission spectrum or absorption spectrum observed in light
• The frequency spectrum of a signal
  • The power spectrum of a signal
• The timbre of a musical note

This article needs to be cleaned up to conform to a higher standard of quality. ... Legend: γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves: EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultrahigh frequency VHF = Very high frequency HF = High frequency... The visible spectrum is the portion of the optical spectrum (light or electromagnetic spectrum) that is visible to the human eye. ... A materials emission spectrum is the amount of electromagnetic radiation of each frequency it emits when it is heated (or more generally when it is excited). ... An absorption spectrum is a diagram depicting the wavelengths of electromagnetic radiation absorbed by a material. ... In mathematics, physics and signal processing, the frequency spectrum is a representation of a signal or other function in terms of frequency (in the frequency domain). It is the projection of the function onto a set of sinusoidal basis functions. ... The power spectrum is a plot of the portion of a signals power (energy per unit time) falling within given frequency bins. ... In music, timbre, also timber, (French, IPA /tæmbər/ as in the first two syllables of tambourine) is the quality of a musical note or sound which distinguishes different types of sound production or musical instruments. ...

In pure mathematics

• The spectrum of an operator
• The spectrum of a matrix
• The spectrum of a ring
• The spectrum of a C*-algebra
• A spectrum (homotopy theory)
• The Stone space of a Boolean algebra
• The spectrum of a theory

In functional analysis, the concept of the spectrum of an operator is a generalisation of the concept of eigenvalues, which is much more useful in the case of operators on infinite-dimensional spaces. ... In linear algebra, the eigenvectors (from the German eigen meaning inherent, characteristic) of a linear operator are non-zero vectors which, when operated on by the operator, result in a scalar multiple of themselves. ... In abstract algebra and algebraic geometry, the spectrum of a commutative ring R, denoted by Spec(R), is defined to be the set of all proper prime ideals of R. It is commonly augmented with the Zariski topology and with a structure sheaf, turning it into a locally ringed space. ... The spectrum of a C*-algebra or dual of a C*-algebra A, denoted Â, is the set of unitary equivalence classes of irreducible *-representations of A. We implicitly assume that irreducible representation means non-null irreducible representation, thus excluding trivial (i. ... In mathematics, a spectrum in homotopy theory is an object in a category constructed for the purposes of stable homotopy theory, starting with the category of CW complexes and aiming to make the suspension functor S invertible. ... In mathematics, Stones representation theorem for Boolean algebras, named in honor of Marshall H. Stone, is the duality between the category of Boolean algebras and the category of Boolean spaces, i. ... In model theory, Morleys categoricity theorem is a theorem of Michael D. Morley which states that if a first-order theory is complete in a countable language, then if it is categorical in some uncountable cardinality, it is categorical in all uncountable cardinalities. ...

Proper nouns

• IEEE Spectrum, a magazine
• The ZX Spectrum, a computer
• A management consultancy firm Spectrum Strategy Consultants
• A fictional army in the television series Captain Scarlet
• The Spectrum Awards (Gaylactic Spectrum Awards) are a literary award.
• Spectrum Radio, an AM station based in London.
• Het Spectrum, or "Uitgeverij Het Sectrum", a Dutch publishing house
• Two music groups:
  • Spectrum (band), an Australian group of the 1970s led by Mike Rudd
  • A more recent group headed by Peter Kember
• Three buildings:
  • The Smith Spectrum, a sports arena in Logan, Utah
  • The Wachovia Spectrum, formerly The Spectrum, a sports arena in Philadelphia
  • The Spectrum Leisure Centre, in Guildford, England

IEEE Spectrum is a magazine edited by the Institute of Electrical and Electronics Engineers. ... The Sinclair ZX Spectrum was a home computer released in the United Kingdom in 1982 by Sinclair Research. ... Captain Scarlet and the Mysterons, often referred to in shorthand as simply Captain Scarlet, is a science fiction television series produced by the Century 21 Television company of Sylvia and Gerry Anderson and Lew Grade and first shown in Britain (originally on ATV Midlands, but later the whole of the... The Gaylactic Spectrum Awards are given to works of science fiction, fantasy and horror which explore gay, lesbian, bisexual or transgender topics in a positive way. ... Spectrum was an Australian progressive rock band which formed in Melbourne in 1969 and remained in existence until 1973. ... Peter Kember (born 19 November 1965) is a British musician, more usually known as Sonic Boom. ... Smith Spectrum is a 10,270-seat multi-purpose arena in Logan, Utah. ... Wachovia Spectrum The Wachovia Spectrum (formerly known as the Spectrum, CoreStates Spectrum and First Union Spectrum) is an indoor arena located in Philadelphia, Pennsylvania. ...

See also

• spectre
• cepstrum