# Kerodon

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

Remark 5.1.4.2. In the situation of Definition 5.1.4.1, the morphism $f: X \rightarrow Y$ is a covariant equivalence relative to $S$ if and only if the opposite morphism $f^{\operatorname{op}}: X^{\operatorname{op}} \rightarrow Y^{\operatorname{op}}$ is a contravariant equivalence relative to $S^{\operatorname{op}}$.