A topological space is said to be disconnected space if can be separated as the union of two non-empty disjoint open sets.

In other words, a topological space is said to be a disconnected space if there exist non-empty open sets and such that and . The pair is called the disconnection of .

**Example:**

Show that two point discrete spaces is disconnected.

Let be a two point discrete space, If is any proper subset of , then both and are non-empty open subsets of such that and . This shows that is a disconnection of , so is a disconnected space.

**Examples:**

• is a disconnected.

• with upper limit topology is disconnected, since and are both open sets which form a disconnection of .

• Let be a non-empty set, with topology defined on . Then is a disconnected space.

• Every discrete space with more than one point is disconnected.