Example 9.1.7.6. Let $\kappa $ be a regular cardinal. Then $\kappa \trianglelefteq \kappa $. For example, if $S$ is a $\kappa $-small set, then the singleton $\{ S \} $ is a $\kappa $-small collection of subsets of $S$ which satisfies the requirements of Definition 9.1.7.5.
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$