# Kerodon

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Definition 2.4.1.6. Let $\operatorname{\mathcal{C}}_{\bullet }$ be a simplicial category, and let $f,g: X \rightarrow Y$ be two morphisms in the underlying category $\operatorname{\mathcal{C}}= \operatorname{\mathcal{C}}_0$ having the same source and target. A homotopy from $f$ to $g$ is an edge $h \in \operatorname{Hom}_{\operatorname{\mathcal{C}}}(X,Y)_{1}$ satisfying $d_1(h) = f$ and $d_0(h) = g$.