This second edition of a landmark reference resource—created not only for psychologists, clinicians, students, and professionals from allied mental health professions, but for all interested readers—offers definitive information on the lexicon of the field, including: Almost 26,000 entries offering clear and authoritative definitions—approximately 1,000 more than the first edition; Balanced coverage of 90 subareas, with significantly revised and expanded content especially in the areas of neuroscience, psychopharmacology, lifespan developmental psychology, statistics, experimental design, and many others; Thousands of incisive cross-references that deepen the user's comprehension of related topics; More than 400 brief biographical entries on historical figures in psychology and other related areas—four times more than the first edition; A Guide to the Dictionary and a Quick Guide to Format that explain stylistic and format features; Three appendixes: Institutional and Organizational Entries; Psychological Test and Assessment Instrument Entries; Psychotherapeutic Techniques, Biological Treatments, and Related Entries.