Radon–Nikodym set

In measure theory, the Radon–Nikodym theorem is a fundamental result that provides conditions under which one measure is absolutely continuous with respect to another. Specifically, it deals with the existence of a density function, known as the Radon–Nikodym derivative, that describes how one measure can be expressed in terms of another. A **Radon–Nikodym set** typically refers to a measurable set that is relevant in the context of the Radon–Nikodym theorem.