Example 9.1.7.10. Every regular cardinal $\lambda $ has exponential cofinality $\geq \aleph _0$ (Remark 4.7.3.17), and therefore satisfies $\aleph _0 \trianglelefteq \lambda $ (Corollary 9.1.7.9).
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
Example 9.1.7.10. Every regular cardinal $\lambda $ has exponential cofinality $\geq \aleph _0$ (Remark 4.7.3.17), and therefore satisfies $\aleph _0 \trianglelefteq \lambda $ (Corollary 9.1.7.9).