Definition:Continuous Mapping (Topology)/Set

Definition
Let $T_1 = \struct {S_1, \tau_1}$ and $T_2 = \struct {S_2, \tau_2}$ be topological spaces.

Let $f: S_1 \to S_2$ be a mapping from $S_1$ to $S_2$.

Let $S$ be a subset of $S_1$.

The mapping $f$ is continuous on $S$ $f$ is continuous at every point $x \in S$.