Chiral perturbation theory

The main elements and methods of chiral perturbation theory, the effective field theory of the Standard Model below the scale of spontaneous chiral symmetry breaking, are summarized. Applications to the interactions of mesons and baryons at low energies are reviewed, with special emphasis on developments of the last three years. Among the topics covered are the strong, electromagnetic and semileptonic weak interactions of mesons at and beyond next--to--leading order in the chiral expansion, nonleptonic weak interactions of mesons, virtual photon corrections and the meson--baryon system. The discussion is limited to processes at zero temperature, for infinite volume and with at most one baryon.