  This work represents an extension of the single pion production model
proposed by D. Rein. The model consists of resonant pion production and
nonresonant background contributions coming from three Born diagrams in the
helicity basis. The new work includes lepton mass effects, and nonresonant
interaction is described by five diagrams based on a nonlinear {\sigma} model.
This work provides a full kinematic description of single pion production in
the neutrino-nucleon interactions, including resonant and nonresonant
interactions in the helicity basis, in order to study the interference effect.
