Algebra of sets/Infobox

Algebra of sets
$\mathcal{A}\subseteq\mathcal{P}(X)$ For an algebra of sets, $\mathcal{A}$ on $X$
Defining properties:
1)	$\forall A\in\mathcal{A}[A^C\in\mathcal{A}]$
2)	$\forall A,B\in\mathcal{A}[A\cup B\in\mathcal{A} ]$