  Symmetry energy terms from macroscopic mass formulae are investigated as
generalized polarizabilities of nuclear matter. Besides the neutron-proton
(n-p) symmetry energy the spin dependent symmetry energies and a scalar one are
also defined. They depend on the nuclear densities ($\rho$), neutron-proton
asymmetry ($b$), temperature ($T$) and exchanged energy and momentum ($q$).
Based on a standard expression for the generalized polarizabilities, a
differential equation is proposed to constrain the dependence of the symmetry
energy on the n-p asymmetry and on the density. Some solutions are discussed.
The q-dependence (zero frequence) of the symmetry energy coefficients with
Skyrme-type forces is investigated in the four channels of the particle-hole
interaction. Spin dependent symmetry energies are also investigated indicating
much stronger differences in behavior with $q$ for each Skyrme force than the
results for the neutron-proton one.
