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

(i) | $E, F, G \in \mathcal{F}$ are each a D1109: Measurable set in $M$ |

(ii) | $F, G$ is a D5143: Set partition of $X$ |

Then
\begin{equation}
\mu(E)
= \mu(E \cap F) + \mu(E \cap G)
\end{equation}