Let $M = (X, \mathcal{F}, \mu)$ be a D1158: Measure space such that

(i)	$E_0, E_1, E_2, \ldots \in \mathcal{F}$ are each a D1109: Measurable set in $M$

Then \begin{equation} \mu \left( \bigcup_{n \in \mathbb{N}} E_n \right) \leq \sum_{n \in \mathbb{N}} \mu(E_n) \end{equation}