Theravāda Buddhism is a neologism denoting a variety of historically connected religious traditions. Today these traditions are predominantly spread in Sri Lanka, Myanmar, Thailand, Laos, Cambodia, and parts of Vietnam. More recent communities in other parts of the world (e. g., Europe, the United States, India, Nepal, Australia) are directly or indirectly connected to the traditions of these countries by migration or adaptation processes. These local varieties do not constitute a homogeneous entity. Nevertheless, the use of a common denominator is justified by their interconnected religious histories and a common stock of liturgical, ritual, exegetical, and narrative traditions.
Prior to the 20th century theravāda (or theriya, theravaṃsa) was understood as a nikāya, an institutionalized monastic lineage primarily defined by a specific system of ritual and legal regulations for monks and nuns (the vinaya). This specific lineage became increasingly associated with Sri Lanka during the first millennium ce, while its Indian origins became obscure. Like many other nikāyas, the Theravādins were not uniform in their doctrinal, ethical, and liturgical orientations. The dynamics of local acculturation and active participation in the translocal networks of the ancient “Buddhist World” produced multiple religious expressions and attitudes within the Theravāda monastic lineage through the centuries. Doctrinally, these could range from an exclusive Pāli-based Śrāvakayāna (“Hīnayāna”) approach to the promotion of so-called Mahāyāna and Vajrayāna texts and practices. A series of royally enforced monastic reforms in the 11th and 12th centuries in Sri Lanka strengthened a certain “conservative” camp of the saṅgha and enforced an exclusivist vision of a Theravāda “orthodoxy,” purified from what this group deemed to be inauthentic adulterations of the Buddha’s teaching. This impulse yielded a powerful—though not unchallenged—impact on the further development of Buddhist monasticism in Sri Lanka and, somewhat later, in Southeast Asia. Ultimately they shaped much of the modern ideas about the characteristics of Theravāda Buddhism.
During the first half of the 20th century the nikāya name Theravāda was detached from its technical monastic meaning and became reinterpreted as a type of Buddhism, idealizing the doctrinal content of the canonical scriptures of this lineage—the so-called Pāli Canon—as a binding belief system for all “Theravāda Buddhists,” monastic or lay. In anachronistic extension of this typology, the compound “Theravāda Buddhism” was further understood as the most ancient, or even “original,” form of the Buddhist “creed.”
The adjective form of Theravāda is Theravādin, which can also be used as a noun to denote a follower of Theravāda.