  The definition and derivation of flavor neutrino states in the framework of
standard Quantum Field Theory is reviewed, clarifying some subtle points. It is
shown that a flavor neutrino state that describes a neutrino produced or
detected in a charged-current weak interaction process depends on the process
under consideration and is appropriate for the description of neutrino
oscillations as well as for the calculation of neutrino production or detection
rates. Hence, we have a consistent framework for the description of neutrino
oscillations and interactions in neutrino oscillation experiments. The standard
flavor neutrino states are obtained as approximations which describe neutrinos
in experiments that are not sensitive to the dependence of neutrino
interactions on the neutrino mass differences. It is also shown that the
oscillation probability can be derived either through the usual light-ray time
= distance approximation or through an average of the space-time dependent
oscillation probability over the unobserved propagation time.
