# Category:Axioms/Sigma-Ring Axioms

This category contains axioms related to Sigma-Ring Axioms.

A $\sigma$-ring is a ring of sets which is closed under countable unions.

That is, a ring of sets $\Sigma$ is a $\sigma$-ring if and only if:

$\ds A_1, A_2, \ldots \in \Sigma \implies \bigcup_{n \mathop = 1}^\infty A_n \in \Sigma$

## Pages in category "Axioms/Sigma-Ring Axioms"

The following 3 pages are in this category, out of 3 total.