ISSN 2676-1041 (Print) Second Language Acquisition as a Discipline: A Historical Perspective Dr. Nabaraj Neupane Abstract Second language acquisition (SLA) generates and tests the theories concerning the acquisition of languages other than first language (L1) in different contexts. Even if SLA is a nascent discipline, its history is remarkable and helpful to seek the answers to the questions that researchers are raising in the field of second language or foreign language. Based on this context, this article aims to recount the history of the burgeoning discipline that heavily draws from numerous disciplines like linguistics, psychology, sociolinguistics, psycholinguistics, and so on. To achieve the objective, document analysis method has been used. The analysis and interpretation of the available documents exhibit that the traces of SLA were observed in the studies that address the issue of language transfer. Specifically, the diachronic study proves that the development of the discipline has undergone three evolving phases like background, formative, and developmental. The background phase caters for behaviourism, contrastive analysis hypothesis, and the attacks on the fundamental premises of behaviourism. The formative phase deals with Chomsky’s revolutionary steps, error analysis, interlanguane theory, morpheme order studies, and the Krashen’s monitor model that opened up the avenues for further studies of SLA. The developmental phase recounts various studies that have consolidated SLA as a separate discipline. Keywords: behaviourism, error analysis, interlanguage theory, monitor model, second language Introduction Second Language Acquisition (SLA) is an emerging feld of enquiry, developed from multiple disciplines like psychology, sociology, linguistics, pedagogy and the like (Mitchell & Myles, 2004). It implies that SLA is not unidisciplinary but interdisciplinary as it borrows numerous concepts, views, ideas, theories, and practices from different disciplines. Yet, the nucleus of SLA began from the issue of the role of the native language (NL) in learning other languages. This central phenomenon is termed as language transfer, on which many theoretical underpinnings are associated with (Gass & Selinker, 2009). Thus, the historical overview of SLA revolves around the key issue of language transfer, on which theoreticians have expressed their views for and against the notion. For example, early theorists like behaviourists and contrastive analysts suppose language transfer as a main source of errors whereas the latter theorists in the 1970s and beyond the 1980s denied the key role of language transfer. The post-war history of SLA is crucial to recount because numerous changes occurred after 1950s are responsible for the foundations of SLA as a burgeoning discipline. Therefore, Mitchell and Myles (2004) have divided the history of SLA in three different periods as: the 1950s and 1960s, the 1970s, and the 1980s and beyond. The frst phase witnessed the developments of behaviourism, structuralism and contrastive analysis hypothesis, which frmly believed on the role of NL in the development of SL. The second phase Journal of NELTA Gandaki (JoNG), II, 55-64