This document discusses factors that influence second language variation and acquisition at both the micro and macro social levels. At the micro level, it discusses how contextual dimensions, linguistic contexts like phonology, psychological contexts like attention, and microsocial contexts like formality influence variation. It also discusses how input, interaction, and modifications to interaction are essential for language learning. At the macro level, it discusses how global and national status of languages, boundaries and identities, social institutions, social categories of learners, and circumstances of learning like prior knowledge, social development, and formal vs informal training impact second language acquisition.