  Classification of galaxy spectral energy distributions in terms of orthogonal
basis functions provides an objective means of estimating the number of
significant spectral components that comprise a particular galaxy type. We
apply the Karhunen-Lo\`{e}ve transform to derive a spectral eigensystem from a
sample of ten galaxy spectral energy distributions. These spectra cover a
wavelength range of 1200 \AA\ to 1 $\mu$m and galaxy morphologies from
elliptical to starburst. We find that the distribution of spectral types can be
fully described by the first two eigenvectors (or eigenspectra). The derived
eigenbasis is affected by the normalization of the original spectral energy
distributions. We investigate different normalization and weighting schemes,
including weighting to the same bolometric magnitude and weighting by the
observed distribution of morphological types. Projecting the spectral energy
distributions on to their eigenspectra we find that the coefficients define a
simple spectral classification scheme. The galaxy spectral types can then be
described in terms of a one parameter family (the angle in the plane of the
first two eigenvectors). We find a strong correlation in the mean between our
spectral classifications and those determined from published morphological
classifications.
