  The scalar nonstandard interactions (NSI) can also introduce matter effect
for neutrino oscillation in a medium. Especially the recent Borexino data
prefers nonzero scalar NSI, $\eta_{ee} = - 0.16$. In contrast to the
conventional vector NSI, the scalar type contributes as a correction to the
neutrino mass matrix rather than the matter potential. Consequently, the scalar
matter effect is energy independent while the vector one scales linearly with
neutrino energy. This leads to significantly different phenomenological
consequences in reactor, solar, atmospheric, and accelerator neutrino
oscillations. A synergy of different types of experiments, especially those
with matter density variation, is necessary to identify the scalar NSI and
guarantee the measurement of CP violation at accelerator experiments.
