MathGloss

A sequence xiiN{x_i}_{i\in\mathbb N} in a topological space XX converges to xXx \in X if for every open UXU\subset X such that xUx \in U, there exists n0Nn_0 \in\mathbb N such that for every nn0n \geq n_0, we have xnUx_n \in U.

In a general topological space, (i.e. in some non-Hausdorff spaces) the limit of a sequence need not be unique!