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 psychiatry
• The autistic spectrum, in psychiatry

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
  • The spectral class of stars (astronomy)
  • The spectral class of asteroids (astronomy)
• 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

In pure mathematics

• The spectrum of a matrix is a concept used in linear algebra
• The spectrum of an operator is a concept used in functional analysis (a generalisation of the spectrum of a matrix)
• The spectrum of a ring is a concept in commutative algebra
• The spectrum of a C*-algebra
• A spectrum (homotopy theory)
• The Stone space of a Boolean algebra
• The spectrum of a theory is a concept in mathematical logic

Proper nouns

• IEEE Spectrum, a magazine
• The ZX Spectrum, a computer
• Spectrum Suite of service management products
• A fictional international security organisation in the television series Captain Scarlet
• The Spectrum Awards (Gaylactic Spectrum Awards) are a literary award.
• Spectrum Radio, an AM station based in London.
• Spectral Sound, a record label
• Two companies:
  • Het Spectrum, or "Uitgeverij Het Spectrum", a Dutch publishing house
  • Spectrum Strategy Consultants, a management consulting firm
• 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

See also

• spectre
• cepstrum

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