The Stacks project

Definition 34.3.4. Compare Schemes, Definition 26.5.2. Let $T$ be an affine scheme. A standard Zariski covering of $T$ is a Zariski covering $\{ U_ j \to T\} _{j = 1, \ldots , m}$ with each $U_ j \to T$ inducing an isomorphism with a standard affine open of $T$.