  A classification of leptonic currents with respect to C-operation requires
the separation of elementary particles into the two classes of vector C-even
and axial-vector C-odd character. Their nature has been created so that to each
type of lepton corresponds a kind of neutrino. Such pairs are united in
families of a different C-parity. Unlike the neutrino of a vector type, any
C-noninvariant Dirac neutrino must have his Majorana neutrino. They constitute
the purely neutrino families. We discuss the nature of a corresponding
mechanism responsible for the availability in all types of axial-vector
particles of a kind of flavour which distinguishes each of them from others by
a true charge characterized by a quantum number conserved at the interactions
between the C-odd fermion and the field of emission of the corresponding types
of gauge bosons. This regularity expresses the unidenticality of truly neutral
neutrino and antineutrino, confirming that an internal symmetry of a
C-noninvariant particle is described by an axial-vector space. Thereby, a true
flavour together with the earlier known lepton flavour predicts the existence
of leptonic strings and their birth in single and double beta decays as a unity
of flavour and gauge symmetry laws. Such a unified principle explains the
availability of a flavour symmetrical mode of neutrino oscillations.
