  The notion of the spin is shown to have two constituents, as exemplified by
the spin of the electron. The first one is related to the form of the wave
equation and determines the fermion or boson particle type. This implies the
spin taking strictly half-integer or integer number. The second side of spin
manifestation is related to the physical nature of the spin of the electron
(and the corresponding magnetic moment) in the interaction resulting in
nonuniform motion. It is shown that in this manifestation spin is no more fixed
constant.
