  A brief summary of collective mode excitations that can exist in singlet
superconductors with irreducible representation $L$ is given. Such excitations
may be classified as the coupled excitations of the charge density $\rho$ and
the phase $\phi $ of the order parameter, or of the amplitude $\Delta$ of order
parameter. Each of these classes may be further characterized in the long
wavelength limit by the irreducible representation $\ell$ of the excitation,
which may or may not be the same as the ground state $L$.
