\begin{definition}[Definition:Indiscrete Topology]
Let $S \ne \O$ be a set.
Let $\tau = \set {S, \O}$.
Then $\tau$ is called the '''indiscrete topology''' on $S$.
A topological space $\struct {S, \set {S, \O} }$ is known as an '''indiscrete space'''.
\end{definition}