Expulsion
Pārājika
The rules in this category are known in Pali as pārājika. The exact meaning of the Pali word is disputed, but there is no doubt that it refers to expulsion from the Sangha. There are four such rules for the monks, all of which are shared with the nuns. Anyone who breaches any of these rules immediately loses his status as a monk. He is expelled from the Sangha and ineligible for re-ordination for the rest of his life. The pārājikas, together with the next category of rules, the saṅghādisesas, are collectively known as serious offenses, garukāpatti. These rules are the most fundamental ones for the proper living of the monastic life.
Suspension
Saṅghādisesa
The rules in this category are known in Pali as saṅghādisesa. The meaning of the word is disputed, but according to the commentary it means that the Sangha is required at the beginning (ādi) and for the rest (sesa) of the procedure. There are thirteen such rules for the monks, seven of which are shared with the nuns. Offenders must undergo a period of probation before being rehabilitated to their former status in the Sangha.
Relinquishment with Confession
Nissaggiya Pācittiya
The rules in this category are known in Pali as nissaggiya pācittiya, "entailing relinquishment and confession". There are thirty such rules for the monks, the same number as for the nuns, although only eighteen are held in common. These rules, together with the remaining rules of the Monastic Code, are classed as light offenses, lahukāpatti. For light offenses there is usually no penalty apart from confession. For the nissaggiya pācittiyas, however, any item involved in the committing of an offense must be relinquished. Once the offense has been confessed, the item is, with a few exceptions, returned to the offender.
Confession
Pācittiya
The rules in this category are known in Pali as pācittiya, "entailing confession". There are ninety-two such rules for the monks, seventy of which are shared with the nuns. This is the largest class of rules in the Monastic Code. These rules, together with all the other rules apart from those entailing expulsion and suspension, are classed as light offenses, lahukāpatti. For light offenses there is no penalty apart from confession.
Acknowledgment
Pāṭidesanīya
The rules in this category are known in Pali as pāṭidesanīya, "entailing acknowledgement". There are four such rules for the monks, none of which are shared with the nuns. What distinguishes these rules from the pācittiyas is the manner of confession. For these rules the confession is done using a unique formula, with the second rule being the only one in the Monastic Code where all the offenders confess together as a group.
Rules of Training
Sekhiya
The rules in this category are known in Pali as sekhiya, "involving training". There are seventy-five such rules, and they are the same both for the monks and the nuns. The sekhiyas are mostly rules of etiquette. Breaking a sekhiya is only considered to be a transgression if the offender is acting out of disrespect for the rule.
The Settling of Legal Issues
Adhikaraṇasamatha
There are seven adhikaraṇasamathadhamma, "principles for the settling of legal issues", which are the same for the nuns and the monks. These are not rules in the ordinary sense and as such fall outside of the classification into serious and light offenses. Instead, they set out the proper methods for dealing with legal issues. The detailed explanation for these is found in the Samathakkhandhaka. The legal issues to be settled through these principles fall into four categories: disputes, accusations, offenses, and proceedings. "Proceedings" includes monastic procedures such as ordination and the keeping of the observance day (uposatha).