Definition:Homeomorphism/Topological Spaces/Definition 3

Definition
Let $T_\alpha = \struct {S_\alpha, \tau_\alpha}$ and $T_\beta = \struct {S_\beta, \tau_\beta}$ be topological spaces.

Let $f: T_\alpha \to T_\beta$ be a bijection.

$f$ is a homeomorphism $f$ is both an open mapping and a continuous mapping.

Also see

 * Equivalence of Definitions of Homeomorphic Topological Spaces