# Feynman diagram

A Feynman diagram is a depiction of a possible process in the interaction of several elementary particles. Feynman diagrams are named after the American physicist Richard Feynman, who first introduced them in the 1950s.

Quantum theory assigns to each Feynman diagram the probability amplitude for that process to occur. The total probability is proportional to the square of the sum of the amplitudes of the possible processes, each of which is depicted by a Feynman diagram.