Warning 9.2.2.7. Definition 9.2.2.6 makes sense for every pair of regular cardinals $\kappa \leq \lambda $. However, we will mostly be interested in the case where $\kappa \trianglelefteq \lambda $, in the sense of Definition 9.1.7.5 (compare with Warning 9.2.1.4).
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$