印度小乘教，佛滅之年結集時，分上座大眾之二部。佛滅百年優婆毱多之時，分曇無德部，薩婆多部，彌沙塞部，迦葉遺部，婆麤富羅部之五部。行宗記一上曰：「二部，結集上座大眾二部。五部，橫分五部者是。」三論玄義曰：「言諸部異執者，或二部，或五部。」參照結集條。
The two are the divisions which took place immediately after the Buddha's death into (a) the elder monks or intimate disciples, and (b) the general body of disciples, styled respectively 上座 and 大眾 q.v.; the five are the divisions, which are said to have occurred a century later, into Dharma-guptah 曇無德, Mulasarvastivadah 薩婆多, Mahisasakah 彌沙塞, Kasyapiyah迦葉遺 and Vatsiputriya 姿麤富羅.
一二部五部 佛教最初分裂之根本二部，即上座、大眾二部。佛滅百年，優婆毱多之時，復分曇無德部、薩婆多部、彌沙塞部、迦葉遺部、婆粗富羅部等五部。〔三論玄義、印度之佛教第四章、第六章（印順）〕p318