Example 3.3.4.6. Let $X$ be a discrete simplicial set (Definition 1.1.5.10). Then the maps
\[ \rho _{X}: X \rightarrow \operatorname{Ex}(X) \quad \quad \lambda _{X}: \operatorname{Sd}(X) \rightarrow X \]
are isomorphisms.
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$