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

Jetavanīyas,

Abhayagirivāsins, and

the Mahāvihāravāsins;

(2) Mahāsaṃghika.and the

Pūrvaśailikas,

the Aparaśailikas,

the Lokottara-vāda.and

the Prajñaptivāda;

(3) Sarvāstivāda.and

the Kāśyapīyas,

Mahīśāsakas,

Dharmaguptakas.and the

Mūla-sarvāstivādins; and

(4) Saṃmitīya, and the

Kaurukullaka,

Avantaka, and Vātsīputrīya.

Vinītadeva's list, however, is late and not altogether reliable.

Source

oxfordindex.oup.com