Kl3 and πe3 transition form factors are calculated as an application of DysonSchwinger equations. The role of nonanalytic contributions to the quark–W-boson vertex is elucidated. A one-parameter model for this vertex provides a uniformly good description of these transitions, including the value of the scalar form factor of the kaon at the Callan-Treiman point. The Kl3 form factors, f K ± , are...