  To describe neutrino oscillations in the sense of quantum mechanics and
quantum field theory, we propose to use an off-diagonal neutrino-Higgs (mass)
interaction, as discussed originally in a family gauge theory and in the
extended Standard Model. For neutrino oscillations which take place presumably
between point-like Dirac particles, the proposed description would be unique in
the quantum mechanics sense. This may help us to resolve a few outstanding
puzzles - the question of why there are only three generations, the question of
why the masses of neutrinos are so tiny, the question of why neutrinos
oscillate, and the question of why the dark-matter world is so huge (25%) as
compared to the visible ordinary-matter world (5%).
