This document summarizes language development from infancy through childhood. It discusses the fundamentals of language including sounds, symbols, semantics and syntax. It describes prelinguistic communication in infants and the emergence of first words and sentences between 10-18 months. It also outlines linguistic advances during preschool years including vocabulary growth, grammar acquisition, and private versus social speech. The origins of language development and the relationship between language and thought are examined. Different approaches to children's conversations and language exposure are also summarized.