Definition:Compatible Atlases/Definition 2

Definition
Let $M$ be a topological space.

Let $\mathscr F, \mathscr G$ be $d$-dimensional atlases of class $C^k$ on $M$.

$\mathscr F$ and $\mathscr G$ are $C^k$-compatible every pair of charts $\left({U, \phi}\right) \in \mathscr F$ and $\left({V, \psi}\right) \in \mathscr G$ are $C^k$-compatible.