Fundamental classification of prāṇāyāma. Sahita — with conscious retention — is the basic type taught first. Kevala — absolute, spontaneous — is the advanced state where breathing is suspended naturally.

Sahita requires effort and technique: inhalation (pūraka), retention (kumbhaka), exhalation (recaka). Kevala occurs when prāṇa flows freely through suṣumnā without the need for external breathing.

Both lead to the same destination, but kevala is “supreme” because it represents the natural culmination of the process initiated with sahita.