This document discusses functional approaches to studying second language acquisition (SLA). It outlines four main functional approaches: Systemic Linguistics, Functional Typology, Function-to-form mapping, and Information organization. Systemic Linguistics analyzes language in terms of choices available to express meaning within social contexts. Functional Typology classifies languages based on similarities and differences. Function-to-form mapping views acquisition as a process of grammaticalization from context to lexical items to grammatical markers. Information organization focuses on utterance structure and how learners organize words.