Question

If a topological is a union of disjoint non empty sets then it is said to be

Answer 1

Answer:

Formal definition. A topological space X is said to be disconnected if it is the union of two disjoint non-empty open sets. ... The only subsets of X with empty boundary are X and the empty set. X cannot be written as the union of two non-empty separated sets (sets for which each is disjoint from the other's closure).