Smallest generated σ-algebra

Set

context $X$
postulate $\sigma(A):\equiv \bigcap \{C\ |\ A\subseteq C\land C\subseteq \mathrm{SigmaAlgebra}(X)\} $

Discussion

The smallest σ-algebra over $X$ generated by, and hence containing, $A$.

Reference

Wikipedia: σ-Operator (german)

Parents

Element of

σ-algebra