The bhikkhu-pātimokkha, “the monastic code for monks,” contains the core rules of monastic life in the form of a long list without any explanatory material. There are 227 such rules for the monks, grouped according to the type of offense incurred for breaking the rule, with the exception of the aniyatas (“the undetermined”) and the adhikaraṇasamathadhamma (“the principles for resolving legal issues”), which are principles to be applied rather than rules in the strict sense.
At present the pātimokkha is only found embedded in the Suttavibhaṅga (“the Analysis of the pātimokkha rules”), in which each rule is surrounded by explanatory material. Originally, however, the pātimokkha probably existed as an independent text, known as the pātimokkha-sutta. This can be seen from the fact that rules sometimes refer to other rules that immediately precede them, a connection that is now severed since the Suttavibhaṅga material separates the rules from each other.