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noun (plural spectra |ˈspektrə| or spectrums)

1. a band of colors, as seen in a rainbow, produced by separation of the components of light by their different degrees of refraction according to wavelength.

〘物理〙 スペクトル〘プリズムで太陽光を分解して得られる連続した7色の色帯〙

(the spectrum) the entire range of wavelengths of electromagnetic radiation.

(波動の)範囲

an image or distribution of components of any electromagnetic radiation arranged in a progressive series according to wavelength.

an image or distribution of components of sound, particles, etc., arranged according to such characteristics as frequency, charge, and energy.

2. used to classify something, or suggest that it can be classified, in terms of its position on a scale between two extreme or opposite points:

〖通例単数形で; しばしばthe/a ～ of A〗 A〈意見･問題･気分など〉の(変動)範囲 (!Aが複数C名詞のときでもしばしば単数扱い)

e.g. the left or the right of the political spectrum.

a wide range:

e.g. self-help books are covering a broader and broader spectrum.

diagnosed with or having the characteristics of an autistic spectrum disorder.

offensive displaying traits such as awkwardness in social situations, restricted interests, or repetitive patterns of behavior.

early 17th century (in the sense ‘specter’): from Latin, literally ‘image, apparition’, from specere ‘to look’.