# Definition:Connected (Topology)/Topological Space

## Definition

Let $T = \left({S, \tau}\right)$ be a non-empty topological space.

### Definition 1

$T$ is connected if and only if it admits no separation.

### Definition 2

$T$ is connected if and only if it has no two disjoint nonempty closed sets whose union is $S$.

### Definition 3

$T$ is connected if and only if its only subsets whose boundary is empty are $S$ and $\varnothing$.

### Definition 4

$T$ is connected if and only if its only clopen sets are $S$ and $\varnothing$.

### Definition 5

$T$ is connected if and only if there are no two non-empty separated sets whose union is $S$.

### Definition 6

$T$ is connected if and only if there exists no continuous surjection from $T$ onto a discrete two-point space.

## Also see

• Results about connected spaces can be found here.