The third edition of this encyclopedia continues to break new ground as an important resource for the study of adolescence. Comprehensive in breath and textbook in depth, the third edition – with entries presented in easy-to-access A to Z format – serves as a reference repository of knowledge in the field as well as a frequently updated conduit of new research and knowledge long before such information trickles down to standard textbooks. This updated and expanded major reference work advances the field by pushing and creating new boundaries and areas of study that further our understanding of adolescents and their place in society. The third edition significantly expands the editorial coverage of the encyclopedia with a combination of many new essays as well as significant updates and revisions to most existing entries. Substantively, the third edition continues to draw from four major areas of research relating to adolescence: Self, Identity and Development in Adolescence: This area covers research relating to identity, from early adolescence through emerging adulthood; basic aspects of development (e.g., biological, cognitive, social); and foundational developmental theories. In addition, it focuses on various types of identity including gender, sexual, civic, moral, political, racial, spiritual, religious, and so forth. Adolescents’ Social and Personal Relationships: This area of research examines the nature and influence of various important relationships during adolescence, including family, peer, friends, sexual and romantic as well as significant nonparental adults. Adolescents in Social Institutions: This area of research centers on the influence and nature of important institutions that serve as socializing contexts for adolescents. These major institutions include schools, religious groups, justice systems, medical fields, cultural contexts, media, legal systems, economic structures, and youth organizations. Adolescent Mental Health: This broad area of research focuses on the wide variety of human thoughts, actions, and behaviors relating to mental health from psychopathology to thriving. Major topic examples include deviance, violence, crime, pathology (DSM-5), normalcy, risk, victimization, disabilities, flow, and positive youth development. The Encyclopedia of Adolescence, Third Edition, is an essential reference for advanced undergraduate and graduate students as well as researchers, professors, clinicians, and other practitioners across such related disciplines as developmental psychology, criminology and criminal Justice, child and adolescent psychiatry, clinical child and school psychology, family, and public health.