Remark 9.3.2.16. Let $\operatorname{\mathcal{C}}$ be an $\infty $-category. An object $X \in \operatorname{\mathcal{C}}$ is subterminal if and only if the diagram
\[ X \xleftarrow { {\operatorname{id}}_ X } X \xrightarrow { {\operatorname{id}}_{X} } X \]
exhibits $X$ as a product of $X$ with itself. See Remark 9.3.1.10.