  The 2dF Galaxy Redshift Survey has already yielded over 130,000 galaxy
spectra (out of the planned 250,000). We present a method for the
parameterisation of galaxy spectra in the 2dF and other large redshift surveys
using a new continuous parameter eta=0.44pc1 - pc2, based on a Principal
Components Analysis (where pc1 and pc2 are the projections onto the first and
second principal components respectively). This parameter is designed to be
robust to instrumental uncertainties and it represents the absorption/emission
strength of a galaxy.
