  After hypercharge $Y$, isospin $I$, isospin projection $I_3$, and four
flavour quantum numbers ($S$, $C$, $B^*$ and $T$), weak isospin $I_{w3}$ and
weak hypercharge $Y_w$ in the electroweak theory are substituted by fermion
quantum number $F$ and unit electroweak charge $F_0$, both of which are
conserved in electromagnetic interaction, weak interaction and strong
interaction. Electrical charge $Q$ and neutral current weak charge $Q_Z$ in
electroweak interaction can be expressed by mixture of $F$ and $F_0$ via the
Weinberg angle $\theta_W$. Electroweak interaction is separated into two parts:
one is neutral current electroweak interaction which has no change of particle
types with only exchange of neutral bosons, and the other is charged current
weak interaction which has change of particle types, i.e., decays.
