This document defines key concepts related to child and adolescent development. It discusses that development occurs in physical, cognitive, and psychosocial domains from conception through adulthood. The stages of development include prenatal, infancy, babyhood, childhood, adolescence, and adulthood. Development proceeds at varying rates in different areas for each child. Modern principles of development state that it is lifelong, multidimensional, influenced by both biology and culture, shows plasticity, and is influenced by historical and cultural contexts.