The Stacks project

Definition 76.55.1. Let $S$ be a scheme. Let $f : X \to Y$ be a morphism of algebraic spaces over $S$. We say $f$ is at-worst-nodal of relative dimension $1$ if the equivalent conditions of Morphisms of Spaces, Lemma 67.22.1 hold with $\mathcal{P} =$“at-worst-nodal of relative dimension $1$”.