The Stacks project

Definition 76.6.1. Let $i : Z \to X$ be an immersion. The conormal algebra $\mathcal{C}_{Z/X, *}$ of $Z$ in $X$ or the conormal algebra of $i$ is the quasi-coherent sheaf of graded $\mathcal{O}_ Z$-algebras $\bigoplus _{n \geq 0} \mathcal{I}^ n/\mathcal{I}^{n + 1}$ described above.