| context | $\Sigma \in \mathrm{SigmaAlgebra}(X) $ |
| definiendum | $ \mu\in \mathrm{measure}(\Sigma)$ |
| context | $E\in \Sigma$ |
| context | $S\in \mathrm{Sequence}(\Sigma)$ |
| inclusion | $\mu:\Sigma\to \overline{\mathbb R} $ |
| postulate | $ \mu(E)\ge 0$ |
| postulate | $ \mu(\emptyset)=0 $ |
| postulate | $ \mu\left(\bigcup_{j=1}^\infty S_j\right)=\sum_{j=1}^\infty \mu(S_j) $ |
Wikipedia: Measure