Unique rules when forming that grammar are highlighted like this.
Example sentences follow these rules too!
Joining and Nesting Markers:
Verb[た/る] - means that dictionary form and ta form are accepted.
Verb[causative[て]] - means て form of the causative form of the verb.
にたえない is a phrase literally meaning "cannot bear to". It is used when one cannot look at/ listen to/read something because it is dreadful or in some way unpleasant (often brutal).
Affirmative form (にたえる) is used when something is worth doing. にたえない is also used (usually in the polite form, as に絶えません) with words expressing feelings to show their extreme degree 感謝にたえません (my deepest gratitude).