Let (X,Σ)(X,\Sigma)(X,Σ) be a measurable space with μ\muμ a signed measure. The negative variation of μ\muμ is the function ν\nuν given by ν(A)=π(A)−μ(A)\nu(A) = \pi(A)-\mu(A)ν(A)=π(A)−μ(A) where π\piπ is the positive variation of μ\muμ.