 Monotone class theorem

The monotone class theorem says that the smallest monotone class containing an algebra of sets equals the sigma-algebra generated by that algebra. It extends identities proved on a generating algebra to the full sigma-algebra.

The Monotone Class Theorem is an important result in measure theory, particularly in the theory of σ-algebras and the construction of measures. It provides a way to extend certain types of sets (often related to a σ-algebra) under specific conditions. The theorem is usually stated in terms of the construction of σ-algebras from collections of sets.