  We derive a classification and a measure of classical- and
quantum-correlation of multipartite qubit, qutrit, and in general, $n$-level
systems, in terms of SU$(n)$ representations of density matrices. We compare
the measure for the case of bipartite correlation with concurrence and the
entropy of entanglement. The characterization of correlation is in terms of the
number of nonzero singular values of the correlation matrix, but that of mixed
state entanglement requires additional invariant parameters in the density
matrix. For the bipartite qubit case, the condition for mixed state
entanglement is written explicitly in terms of the invariant paramters in the
density matrix. For identical particle systems we analyze the effects of
exchange symmetry on classical and quantum correlation.
