The Nippon Decimal Classification (NDC, also called the Nippon Decimal System) is a system of library classification developed for mainly Japanese-language books maintained and revised by the Japan Library Association since 1948. Originally developed in 1929 by Kiyoshi Mori, the 10th and latest edition of this system was published in 2014. The decimal notation system is similar to the Dewey Decimal System, and the order of main classes is inspired from the Cutter Expansive Classification. The system is based upon using a three digit number to classify subjects, where more digits can be added if necessary and a decimal point is used to separate the third and fourth digit. The first division level is called a class, the second level is called a division, and the third level is called a section. Each '1-9' digit is used to represent a specific category, with the digit '0' being used to represent general works.

Main classes

The system is made up of ten categories:

Description of the Divisions

000 General

The General category contains books that contain general information, rather than information about specific topics. The sub-categories of the General category are:

100 Philosophy

The Philosophy category contains books that contain information regarding philosophy, religion, and psychology. The sub-categories of the Philosophy category are:

200 History

The History category contains books that contain information regarding local and foreign history. The sub-categories of the History category are:

300 Social Sciences

The Social Sciences category contains books that contain information regarding modern day society, such as government systems and cultural traditions. The sub-categories of the Social Sciences category are:

400 Natural Sciences

The Natural Sciences category contains books that contain information regarding the natural world, such as plants, animals, and natural laws, such as math and physics. The sub-categories of the Natural Sciences category are:

500 Technology and Engineering

The Technology & Engineering category contains books that contain information regarding man-made scientific achievements. The sub-categories of the Technology & Engineering category are:

600 Industry and Commerce

The Industry and Commerce category contains books that contain information regarding business, products, transportation systems, and money. The sub-categories of the Industry and Commerce category are:

700 Arts

The Arts category contains books that contain information regarding various art forms, such as paintings, writing, and music. The sub-categories of the Arts category are:

800 Language

The Language category contains books that contain information regarding various languages spoken around the world. The sub-categories of the Language category are:

900 Literature

The Literature category contains books with fictional content, such as romance novels and adventure stories. The sub-categories of the Literature category are: