Sarbassova G.A.2026-02-062026-02-062012Sarbassova G.A. / Developmental Stages in Second Language Acquisition / Suleyman Demirel University/ СДУ хабаршысы, 12(3 ).https://repository.sdu.edu.kz/handle/123456789/2457This study examines the developmental stages in second language acquisition (SLA). SLA distinguishes between unconscious acquisition, as in children, and conscious learning of rules. L2 acquisition is shaped by universal language principles and structural influences from L1. Socio-psychological factors, such as attitude, motivation, and social distance, play a critical role in learning. The study discusses the advantages and limitations of longitudinal and cross-sectional research. Additionally, Processability Theory (PT) and Organizational Grammar (OG) models are compared to explain developmental stages, highlighting the impact of linguistic structures and learners’ strategies.enAttribution-NonCommercial-ShareAlike 4.0 Internationalsecond language acquisitiondevelopmental stagessocio-psychological factorsProcessability TheoryOrganizational GrammarArticle