Continuous spectrum

From Glossary of Meteorology

continuous spectrum

A spectrum in which wavelengths (and wavenumbers and frequencies) are represented by the continuum of real numbers (or a portion thereof) rather than by a discrete sequence of numbers.

A continuous function on an infinite interval, even though the function is nonzero over only a finite interval, must be represented by the Fourier transform rather than by Fourier series, and the resulting spectrum will be continuous.
See also discrete spectrum.