Eighteen Schools of Early Buddhism
As Buddhism spread throughout India.a diversity of schools developed over the first 400 years, some based on major doctrinal differences and others merely as regional variants.
Retrospectively, various Mahāyāna scholar-monks determined that there were eighteen of these schools, although their accounts of the relationship and differences between them are not consistent. One simple classification, acording to Vinītadeva, has the following four major schools with their offshoots:
(1) Sthavira.and the
Abhayagirivāsins, and
the Mahāvihāravāsins;
(2) Mahāsaṃghika.and the
the Aparaśailikas,
the Lokottara-vāda.and
the Prajñaptivāda;
(3) Sarvāstivāda.and
the Kāśyapīyas,
Dharmaguptakas.and the
Mūla-sarvāstivādins; and
(4) Saṃmitīya, and the
Avantaka, and Vātsīputrīya.
Vinītadeva's list, however, is late and not altogether reliable.
