Sigma-1 formula
= Sigma-1 formula
{c}
{wiki=Arithmetical_hierarchy}
A $\Sigma_1$ formula is equivalent to $\exists\mathbf y\,\delta$ with $\delta$ bounded. A $\Pi_1$ formula is equivalent to $\forall\mathbf y\,\delta$ with $\delta$ bounded.
= Sigma-1 formula
{c}
{wiki=Arithmetical_hierarchy}
A $\Sigma_1$ formula is equivalent to $\exists\mathbf y\,\delta$ with $\delta$ bounded. A $\Pi_1$ formula is equivalent to $\forall\mathbf y\,\delta$ with $\delta$ bounded.