A signed measure on the measurable space (X,Σ)(X,\Sigma)(X,Σ) is a function μ:Σ→R∪{−∞} or R∪{∞}\mu: \Sigma \to \mathbb R \cup \{-\infty\} \text{ or } \mathbb R \cup \{\infty\}μ:Σ→R∪{−∞} or R∪{∞} such that μ(∅)=0\mu(\emptyset) =0μ(∅)=0 and μ\muμ is σ-additive. Note that μ\muμ cannot take on both −∞-\infty−∞ and ∞\infty∞ as values.
Wikidata ID: Q1764371