The rules of discipline first laid down by the Buddha are called Mulapannattt (the root regulation); those supplemented later are known as Anupannatti. Together they are known as Sikkhapadas, rules of discipline. The act of transgressing these rules of discipline, thereby incurring a penalty by the guilty bhikkhu, is called Apatti, which means 'reaching, committing'.
The offences for which penalties are laid down may be classified under seven categories depending on their nature:
An offence in the first category of offences, Parajika f is classified as a grave offence, garukapatti, which is irremediable, atekiccha and entails the falling off of the offender from bhikkhuhood.
An offence in the second category, Samghddisesa, is also classified as a grave offence but it is remediable, satekicchd The offender is put on a probationary period of penance, during which he has to undertake certain difficult practices and after which he is rehabilitated by the Samgha assembly.
The remaining five categories consist of light offences, lahukdpatti, which are remediable and incur the penalty of having to confess the transgression to another bhikkhu. After carrying out the prescribed penalty, the bhikkhu transgressor becomes cleansed of the offence.