What is the meaning of -adh?

Creates the regular verbal noun of first-conjugation verbs.

Autonomous ending of first-conjugation verbs in the past indicative tense.

Analytic ending of first-conjugation verbs in the past habitual tense

Analytic ending of first-conjugation verbs in the past subjunctive mood

Third-person singular ending of first-conjugation verbs in the imperative mood

Regular verbal noun ending.

Autonomous ending of verbs in the past indicative tense

Analytic ending of verbs in the conditional tense

Third-person singular ending of verbs in the imperative mood

Source: wiktionary.org