A biographical dictionary is a book or collection of books containing summaries of the lives of notable individuals, usually arranged alphabetically. Synonyms for biographical dictionary include biographical encyclopedia, biographical reference work, and biographical compendium. Other similar terms include who's who, directory of notable people, and genealogical register. Each of these terms refers to a publication that provides information about individuals' personal and professional lives, achievements, and contributions. These sources are often used by researchers, historians, and genealogists to uncover details about people throughout history who have made significant impacts. Regardless of what term is used, these collections provide valuable insights into the personal and historical contexts of notable figures.