b : kinds of organisms associated with a particular situation (as an environment)

a : a continuum of color formed when a beam of white light is dispersed (as by passage through a prism) so that its component wavelengths are arranged in order

b : any of various continua that resemble a color spectrum in consisting of an ordered arrangement by a particular characteristic (as frequency or energy): as (1) : electromagnetic spectrum (2) : radio spectrum (3) : the range of frequencies of sound waves (4) : mass spectrum

a : a continuous sequence or range [a wide spectrum of interests] [opposite ends of the political spectrum]