The Stacks project

Definition 74.14.1. Let $S$ be a scheme. Let $\mathcal{P}$ be a property of morphisms of algebraic spaces over $S$. Let $\tau \in \{ fpqc, \linebreak[0] fppf, \linebreak[0] syntomic, \linebreak[0] smooth, \linebreak[0] {\acute{e}tale}\}$. We say $\mathcal{P}$ is $\tau$ local on the source, or local on the source for the $\tau$-topology if for any morphism $f : X \to Y$ of algebraic spaces over $S$, and any $\tau$-covering $\{ X_ i \to X\} _{i \in I}$ of algebraic spaces we have