The 2dF Galaxy Redshift Survey has already yielded over 135,000 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 = 0.44 pc _ { 1 } - pc _ { 2 } , based on a Principal Components Analysis ( where pc _ { 1 } and pc _ { 2 } 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 .