Kerodon

$\Newextarrow{\xRightarrow}{5,5}{0x21D2}$ $\newcommand\empty{}$
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$

Notation 1.1.2.12. Let $\operatorname{{\bf \Delta }}_{\operatorname{surj}}$ denote the category whose objects are the linearly ordered sets $[n] = \{ 0 < 1 < \cdots < n \} $ for $n \geq 0$, and whose morphisms are nondecreasing surjective functions $[m] \twoheadrightarrow [n]$.