# Kerodon

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Example 1.4.2.14. Let $\operatorname{\mathcal{C}}$ be an $\infty$-category. If we refer to a commutative diagram $\sigma :$

$\xymatrix { & Y \ar [dr]^{g} & \\ X \ar [ur]^{f} \ar [rr]^{h} & & Z, }$

then we mean that $\sigma$ is a $2$-simplex of $\operatorname{\mathcal{C}}$ satisfying $d_0(\sigma ) = g$, $d_1(\sigma ) =h$, and $d_2(\sigma ) = f$. In other words, we mean that $\sigma$ is a $2$-simplex which witnesses $h$ as a composition of $f$ and $g$, in the sense of Definition 1.3.4.1.