Definition:Convergent Sequence/Topology/Definition 1

Definition
Let $T = \struct {S, \tau}$ be a topological space.

Let $\sequence {x_n}_{n \in \N}$ be an infinite sequence in $S$.

Then $\sequence {x_n}$ converges to the limit $\alpha \in S$ :
 * $\forall U \in \tau: \alpha \in U \implies \paren {\exists N \in \R_{>0}: \forall n \in \N: n > N \implies x_n \in U}$