A set function μ is finitely additive if, given any finite disjoint collection of sets {E_k}_(k = 1)^n on which μ is defined, μ( union _(k = 1)^n E_k) = sum_(k = 1)^n μ(E_k).

countable additivity | countable subadditivity | disjoint union | finite subadditivity | set function