The Stacks project

Definition 67.31.2. Let $S$ be a scheme. Let $f : X \to Y$ be a morphism of algebraic spaces over $S$. Let $\mathcal{F}$ be a quasi-coherent sheaf on $X$.

1. Let $x \in |X|$. We say $\mathcal{F}$ is flat at $x$ over $Y$ if the equivalent conditions of Lemma 67.31.1 hold.

2. We say $\mathcal{F}$ is flat over $Y$ if $\mathcal{F}$ is flat over $Y$ at all $x \in |X|$.