# Kerodon

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

Example 2.2.3.3. Let $\operatorname{\mathcal{C}}$ be a monoidal category, and let $B\operatorname{\mathcal{C}}$ be the $2$-category obtained by delooping $\operatorname{\mathcal{C}}$ (Example 2.2.2.5). Then the opposite $2$-category $(B\operatorname{\mathcal{C}})^{\operatorname{op}}$ can be identified with $B(\operatorname{\mathcal{C}}^{\operatorname{rev}})$, where $\operatorname{\mathcal{C}}^{\operatorname{rev}}$ denotes the reverse of the monoidal category $\operatorname{\mathcal{C}}$ (Example 2.1.3.5).