A biographical dictionary is a reference book that provides concise information about the lives of notable individuals. It typically includes details such as birth and death dates, significant achievements, and contributions to their fields. These dictionaries can cover a wide range of subjects, including politicians, artists, scientists, and historical figures. Biographical dictionaries are useful for researchers, students, and anyone interested in learning about influential people. They often organize entries alphabetically and may include cross-references to related individuals or topics, making it easier to explore connections between different figures, such as Albert Einstein and Isaac Newton.