Samāpatti is a common term for both Theravada Buddhism and Hindu Yoga, quodammodo also for Jainism, frequently used as a synonym for samādhi. Samāpatti stands for correct (samyag) acquisition (āpatti) of Truth. It is a form of alaukika-pratyakṣa (extraordinary perception) forming thus a legitimate part of the perceptual (pratyakṣa) instruments of adequate knowledge (pramāṇa).
In the Pātañjala Yoga, samāpatti is discussed as the universal form of the Yoga called samprajñāta-yoga, or cognitive Yoga, followed by asamprajñāta-yoga, or transcognitive Yoga. It has as its prerequisite the annihilation of all (non-sattvic) modifications (vṛtti) of consciousness (citta).
There are four realms and eight stages of samāpatti.
I. The coarse (sthūla) realm of the physical mahābhūta world down to the triple atoms (tryaṇuka) and possibly molecules (dvyaṇuka) is covered by
II. The subtle (sūkṣma) world of the atoms and their constituents (tanmātras) down to the primary material (prakritic) "soap" out of which everything physical evolves (bhūtādi) is cognized in two steps:
4. Nirvicāra-samāpatti (certain knowledge without whatsoever hesitations, vicikitsā).
The state of the nirvicāra-samāpatti is also known as the dharmamegha, Dharma Cloud, where the truths about this world start pouring like a rain.
6. Nirānanda-samāpatti, reduction of the pure cognitive ānanda as hampering the further progress of the sādhaka on the way to the final liberation.
IV. The realm of the last fight with samsāra, where one should destroy the very feeling of I-am (aham asmi, ego sum):
7. Sāsmitā-samāpatti, the sphere of action of the Cartesian Cogito ergo sum which brings the Transcendental Self (Ātman) to wrong identifications with the pure sattvic evolutes of prakṛti, i.e., with manas-sattva.
8. Nirasmitā-samāpatti, acquisition of that final stage of meditation where there is no more wrong self-identifications (abhimāna) and the form of the Seer (Draṣṭṛ) coincides with the own-form of Puruṣa, thus allowing Patañjali to say, "then Draṣṭṛ is established in its own form" (Yoga-sūtra I.3).
Methodologically, from the point of view of their certainty and veridicality, the eight samāpattis can be represented in two formal groups:
1. Savikalpa-samādhi (samāpatti 1, 3, 5, and 7)
2. Nirvikalpa-samādhi (samāpatti 2, 4, 6, and 8)