By Buddhadasa Bhikkhu
The Sangha of everyday language is the assembly of monks themselves. The Sangha of Dhamma language are those high qualities in the minds of the monks. The Sangha proper consists of these four levels: the stream-enterer (sota-panna), the once-returner (sakadagami), the non-returner (anagami), and the fully perfected being (arahant, worthy one, undefiled by any egoism), These terms, too, refer to mental rather than physical qualities, because the physical frames of these people are in no way different from those of anyone else. Where they do differ is in mental or spiritual qualities. This is what make a person a stream-enterer, once-returner, non-returner, or arahant. This is how the word "Sangha" is to be understood in Dhamma language.