spectra

Multiple Entries:
  spectra    spectrum  

Concise Oxford English Dictionary © 2008 Oxford University Press:
spectra/ˈspektrə/

plural form of spectrum.

Concise Oxford English Dictionary © 2008 Oxford University Press:
spectrum/ˈspektrəm/

▶noun (pl. spectra /-trə/)

• 1 a band of colours produced by separation of the components of light by their different degrees of refraction according to wavelength, e.g. in a rainbow.

  ■ the entire range of wavelengths of electromagnetic radiation.

  ■ a characteristic series of frequencies of electromagnetic radiation emitted or absorbed by a substance.

  ■ the components of a sound or other phenomenon arranged according to frequency, energy, etc.

• 2 a scale extending between two points; a range: the political spectrum.

– origin C17 (in the sense ‘spectre’): from L., lit. ‘image, apparition’, from specere ‘to look’.