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

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

Then \begin{equation} \mu \left( \bigcup_{n = 1}^N E_n \right) < \infty \quad \iff \quad \mu(E_1), \ldots, \mu(E_N) < \infty \end{equation}