Let $M = (X, \mathcal{F})$ be a D1108: Measurable space.
A D1109: Measurable set $E \in \mathcal{F}$ is an atomic measurable set in $M$ if and only if

(1)	\begin{equation} E \neq \emptyset \end{equation}
(2)	\begin{equation} \forall \, F \in \mathcal{F} \left( F \subseteq E \quad \implies \quad F = \emptyset \text{ or } F = E \right) \end{equation}