= Solution
A bounded <quantifier> has the form $\exists u\in v$ or $\forall u\in v$, abbreviating $\exists u(u\in v\wedge\cdots)$ or $\forall u(u\in v\to\cdots)$. A $\Sigma_0$ <logical formula>, also called $\Delta_0$, is built from atomic membership and equality <logical formulas> using Boolean connectives and only bounded <quantifiers>. It has no unbounded <quantifier>.
For example $z\subseteq y$ abbreviates the bounded <logical formula> $\forall u\in z\,(u\in y)$. <Quantifiers> are bounded by an existing variable or parameter, not by an unrestricted <class term> such as the <power set> of a parameter unless that <set> has separately been supplied as a parameter.
Back to article page
