The third chapter contains conjugation rules for building (active voice) verbs that have a certain verb ending. By that, for example all verbs ending on "venire" are conjugated following the rules of the ~venire-conjugation.
Verb-endings:
also see
Chapter 1: General Information
Chapter 2: the regular verbs
Chapter 3: the irregular verb endings, active voice
Chapter 4: the irregular verb endings, passive voice
Chapter 5: the irregular verbs
Chapter 6: deponent- and semi-deponent verbs
Chapter 7: Appendix