In measure theory, a branch of mathematics, a continuity set of a measure μ is any Borel set B such that
\mu(\partialB)=0,
where
\partialB
|\mu|(\partialB)=0.
The class of all continuity sets for given measure μ forms a ring.[1]
Similarly, for a random variable X, a set B is called continuity set if
\Pr[X\in\partialB]=0.
The continuity set C(f) of a function f is the set of points where f is continuous.