Book excerpt: This book provides concise definitions for some 700 terms used in the diagnosis & classification of mental discorder. Now in its second edition, the lexicon has been revised & expanded to meet the practical need, in clinical work, teaching & research, for an explicit & authoritiative lexis of terms used in the chapter on mental & behavioral disorders of the 10th revision of the INTERNATIONAL STATISTICAL CLASSIFICATION OF DISEASES & RELATED HEALTH PROBLEMS(ICD-10). Most of the terms have been newly defined for the second edition, in line with the extensive revisions incorporated in ICD-10. Each term is defined as precisely & concisedly as possible. Where appropriate, the code number of the ICD-10 category in which the term appears is given as part of the entry. Alternative names, synonyms, & near-synonyms are also included. The lexicon represents a major step toward the achievement of an internationally-accepted nomenclature for mental disorders & should find wide application in clinical, teaching & research settings.