The Dewey Decimal Classification (DDC) system is a library classification system used to organize books and other materials in libraries. The system is based on a numerical system, with each number representing a specific subject area. The following are the main sections of the Dewey Decimal Classification system:

000-099: General Works 100-199: Philosophy and Psychology 200-299: Religion 300-399: Social Sciences 400-499: Language 500-599: Natural Sciences and Mathematics 600-699: Technology and Applied Sciences 700-799: Arts and Recreation 800-899: Literature 900-999: History and Geography

Each of these sections is further divided into subcategories, allowing for more specific classification of materials. For example, the 300-399 section on Social Sciences includes subcategories such as sociology, economics, and political science.