Example 1.4.4.4. Let $\operatorname{\mathcal{C}}$ be an ordinary category containing a pair of morphisms $f: X \rightarrow Y$ and $g: Y \rightarrow Z$. Then there is a unique morphism $h: X \rightarrow Z$ in the $\infty $-category $\operatorname{N}_{\bullet }(\operatorname{\mathcal{C}})$ which is a composition of $f$ and $g$, given by the usual composition $g \circ f$ in the category $\operatorname{\mathcal{C}}$.
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$