Fermion generation

A generation groups corresponding quarks and leptons with the same gauge quantum numbers as their counterparts in other generations. The Standard Model has three such families. Yukawa matrices assign their different masses, and the mismatch of up-type and down-type mass bases produces the CKM matrix.

The three quark generations pair $(u,d)$, $(c,s)$ and $(t,b)$, each containing one charge-$2/3$ and one charge-$-1/3$ quark. The number of generations controls the number of physical mixing angles and CP-violating phases in the CKM matrix.