# Kerodon

$\Newextarrow{\xRightarrow}{5,5}{0x21D2}$ $\newcommand\empty{}$

Definition 3.1.4.1. Let $f: X \rightarrow S$ be a morphism of simplicial sets. We say that $f$ is a covering map if, for every pair of integers $0 \leq i \leq n$ with $n > 0$, every lifting problem

$\xymatrix@R =50pt@C=50pt{ \Lambda ^{n}_{i} \ar [r] \ar@ {^{(}->}[d] & X \ar [d]^{f} \\ \Delta ^ n \ar [r] \ar@ {-->}[ur] & S }$

has a unique solution.