The Early Buddhist schools are those schools of Buddhism which accept only the scriptures which correspond to the Suttapitaka, Vinayapitaka and (possibly) an Abhidhammapitaka. These schools of Buddhism do not recognize or accept the Mahayana Sutras as the word of Buddha. Examples of these schools are pre-sectarian Buddhism, the early Buddhist schools, and any possible other schools or views in which the historical Tipitaka represents the scripture with the highest authority. Some scholars use the term as excluding pre-sectarian Buddhism.
Hinayana or Nikāya Buddhism is distinguished from the Buddhism of the various Mahāyāna and Vajrayāna schools, which accept the authenticity of a range of other scriptures as spoken by Buddha (mainly the Mahayana Sutras). Many of the sutras corresponding to those of the Pāli Canon are accepted by every school.
Historically, there were many 'Nikāya schools', but only one still exists today in (close to) its original form: the Theravāda. Mahayana and Vajrayana Buddhism use the ordination lineages of these schools. There were once at least eighteen Nikāya schools (for some lists see early Buddhist schools).
Many commentors on Buddhism have used the term Hīnayāna to refer to Nikāya Buddhism. However, that term is now generally seen as flawed:
According to Robert Thurman, the term "Nikāya Buddhism" was coined by Professor Masatoshi Nagatomi of Harvard University, as a way to avoid the usage of the term Hinayana . "Nikaya Buddhism" is thus an attempt to find a more neutral way of referring to Buddhists who follow one of the early Buddhist schools, and their practice. The term Śrāvakayāna (literally, "hearer vehicle" or "disciples' vehicle") is also sometimes used for the same purpose. Other terms that have been used in similar senses include sectarian Buddhism, conservative Buddhism and mainstream Buddhism (this last might be considered derogatory by Mahayanists, as implying that they are fringe). Note that Nikāya is also a term used in Theravāda Buddhism to refer to a subschool or subsect within Theravada.
Like the term Hinayana Buddhism, the term Nikaya Buddhism focuses on the presumed commonality between the schools, and not on the actual schools themselves. This commonality is thought to be found in a certain attitude. The difference is that in 'Hinayana Buddhism' the common attitude was stated to be a certain 'selfishness', while the term 'Nikaya Buddhism' tries to shift the attention to the more neutral issue of attitude concerning the authenticity of scriptures.
Some disadvantages of the term Nikaya Buddhism are:
The bodhisattva ideal in Theravada Buddhist theory and practice: a reevaluation of the bodhisattva-sravaka opposition.
Jul 01, 1997; In the academic study of Buddhism the terms "Mahayana" and "Hinayana" are often set in contradiction to each other, and the two...