linguistic:translation, structural:expansion
Countable subadditivity

For any countable sequence E 1, E 2, E 3, … {\displaystyle E_{1},E_{2},E_{3},\ldots } of (not necessarily disjoint) measurable sets E n {\displaystyle E_{n}} in Σ: {\displaystyle \Sigma :} μ (⋃ i = 1 ∞ E i) ≤ ∑ i = 1 ∞ μ (E i). {\displaystyle \mu \left(\bigcup _{i=1}^{\infty }E_{i}\right)\leq \sum _{i=1}^{\infty }\mu (E_{i}).}