Hello, Something I have some time wondering and still couldn't find the answer is to this question: if there is some relation between the Spectrum (functional analysis) and the Frequency spectrum in Fourier Analysis. Now that I think about it there seems to be a casuality the use of the same word spectrum, without any relation of one concept to the other, but when I asked my linear algebra teacher if there was some relation between (eigenvectors/eigenvalues) and the fourier transform she told me yes, without any more info as to what was that relation. Any ideas? Pure coincidence? Heavily related? Hints? Thanks!