■ noun ( plural 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 ~.
Origin
C17 (in the sense 'spectre'): from L., lit. 'image, apparition', from specere 'to look'.