The book explores the theoretical and philosophical groundings of various frameworks of language acquisition, pedagogy and practices. Central to its inquiry are foundational questions such as: How do different theories look at the nature of language and its acquisition, and how do they generate a two-way process of influencing pedagogical practices in different socio-cultural contexts and receive information back from the practices for its theoretical reflections? Structured in five parts—(i) Linguistic structure, language use, and cognitive processes; (ii) Cultural embeddedness of linguistic structures; (iii) The acquisition-learning debate and contemporary language pedagogy; (iv) Multilingual contexts of language use and instruction; and (v) The socio-political epistemology of language use—the book engages in a socio-political and critical-historical analysis. It traces the evolution of linguistic concepts and their influence on educational practices, explores their transdisciplinary migration across linguistics, psychology, and education, and interrogates the conceptual tensions that continue to challenge and reshape the field of language learning and pedagogy.