Kerodon

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

Remark 1.1.2.10. Roughly speaking, one can think of the horn $\Lambda ^{n}_{i}$ as obtained from the $n$-simplex $\Delta ^ n$ by removing its interior together with the face opposite its $i$th vertex (see Example 1.1.8.13).