2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/199999I discuss the problem of formulating the baryon chiral perturbation theory ($χ$PT) in the presence of a light resonance, such as the $Δ(1232)$, the lightest nucleon resonance. It is shown how to extend the power counting of $χ$PT to correctly account for the resonant contributions. Recent applications of the resulting chiral effective-field theory to the description of pion production reactions in $Δ$-resonance region are briefly reviewed.8 pages, 8 figs; prepared for the proceedings of the Intl Erice School ``Quarks in Hadrons and Nuclei'', 29th Course, 16--24 Sep 2007, Sicily, ItalyNuclear Theorytext