Linked from
The 18 pages that link to Cabibbo–Kobayashi–Maskawa matrix, each with the reason it gives.
Standard ModelRelated: Its parameters let the model describe quark mixing and CP violation.
CP violationRelated: Its complex phase produces CP-violating differences among quark transitions.
W and Z bosonsRelated: It determines which quark flavor changes W-boson interactions can produce.
Charm quarkRelated: Its matrix elements determine which weak decays of charm quarks are favored.
KaonRelated: Its elements govern the quark-flavor transitions in many kaon decays.
Yukawa interactionRelated: Quark Yukawa matrices determine the quark masses and this mixing matrix.
Strange particlesRelated: Its flavor-changing couplings govern many strange-hadron decay rates.
Strange quarkRelated: Its elements govern weak transitions involving strange quarks.
Up quarkRelated: It sets the probabilities for weak transitions involving an up quark.
Down quarkRelated: Its elements govern the probabilities of down-quark flavor transitions.
Free neutron decayRelated: Its up-down mixing element contributes to the neutron decay rate.