The four stages of attainment [edit]
The Sangha of the Tathagata's disciples (Ariya Sangha) can be described as including four or eight kinds of individuals. There are four [groups of noble disciples] when path and fruit are taken as pairs, and eight groups of individuals, when each path and fruit are taken separately:
(1) the path to stream-entry; (2) the fruition of stream-entry;
(3) the path to once-returning; (4) the fruition of once-returning;
(5) the path to non-returning; (6) the fruition of non-returning;
(7) the path to arahantship; (
the fruition of arahantship.
Stream-enterer [edit]
Main article: Sot?panna
The first stage is that of Sot?panna (Pali; Sanskrit: Srot?panna), literally meaning "one who enters (?padyate) the stream (sotas)," with the stream being the supermundane Noble Eightfold Path regarded as the highest Dharma. The stream-enterer is also said to have "opened the eye of the Dharma" (dhammacakkhu, Sanskrit: dharmacak?us).
A stream-enterer reaches arahantship within seven rebirths upon opening the eye of the Dharma.
Due to the fact that the stream-enterer has attained an intuitive grasp of Buddhist doctrine (samyagd???i or samm?di??hi, "right view") and has complete confidence or Saddha in the Three Jewels: Buddha, Dharma, and Sangha, that individual will not be reborn in any plane lower than the human (animal, preta, or in hell).
Once-returner [edit]
Main article: Sakadagami
The second stage is that of the Sakad?g?m? (Sanskrit: Sak?d?g?min), literally meaning "one who once (sak?t) comes (?gacchati)". The once-returner will at most return to the human world one more time. Both the stream-enterer and the once-returner have abandoned the first three fetters. The stream-enterer and once-returner are distinguished by the fact that the once-returner has weakened lust, hate, and delusion to a greater degree. The once-returner therefore has fewer than seven rebirths. They may take place in higher planes but will include rebirth in the human world at most only once more. Once-returners do not have only one more rebirth, as the name suggests, for that may not even be said with certainty about the non-returner who can take multiple rebirths in the five "Pure Abodes".
Non-returner [edit]
Main article: An?g?mi
The third stage is that of the An?g?m? (Sanskrit: An?g?min), literally meaning "one who does not (an-) come (?gacchati)". The non-returner, having overcome sensuality, does not return to human world, or any unfortunate world lower than that after death. Instead, non-returners are reborn in one of the five special worlds in R?padh?tu called the ?uddh?v?sa worlds, or "Pure Abodes", and there attain Nirv??a; P?li: Nibbana; some of them are reborn a second time in a higher world of the Pure Abodes.
An An?g?m? has abandoned the five lower fetters, out of ten total fetters, that bind beings to the cycle of rebirth. An An?g?m? is well advanced.
Arahant [edit]
Main article:
Arahant
The fourth stage is that of Arahant, a fully awakened person. He has abandoned all ten fetters and, upon death (Sanskrit: Parinirv??a, P?li: Parinibb?na) will never be reborn in any plane or world, having wholly escaped sa?s?ra.[6] An Arahant had attained awakening by following the path given by the Buddha. In Theravada the term Buddha is reserved for Siddartha Gautama Buddha, as being the one who discovered the path by himself.
http://en.wikipedia.org/wiki/Four_stages_of_enlightenment