  Neutrino decay in vacuum has often been considered as an alternative to
neutrino oscillations. Because non-zero neutrino masses imply the possibility
of both neutrino decay and neutrino oscillations, we present a
model-independent formal treatment of these combined scenarios. For that, we
show for the example of Majoron decay that in many cases decay products are
observable and may even oscillate. Furthermore, we construct a minimal scenario
where we study the physical implications of neutrino oscillations with
intermediate decays.
