Remark 9.3.1.5. Let $\operatorname{\mathcal{C}}$ be an $\infty $-category, and let $X$ and $Y$ be objects of $\operatorname{\mathcal{C}}$. If $X$ is $n$-truncated and $Y$ is a retract of $X$, then $Y$ is also $n$-truncated. In particular, if $X$ and $Y$ are isomorphic, then $X$ is $n$-truncated if and only if $Y$ is $n$-truncated.
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$