Dewey Decimal Classification (DDC) Summaries

The Dewey Decimal Classification (DDC) system is a general knowledge organization tool that is continuously revised to keep pace with knowledge. It is published by OCLC Online Computer Library Center, Inc. OCLC owns all copyright rights in the Dewey Decimal Classification, and licenses the system for a variety of uses.

The DDC is the most widely used classification system in the world. It is built on sound principles that make it ideal as a general knowledge organization tool: meaningful notation in universally recognized Arabic numerals, well-defined categories, well-developed hierarchies, and a rich network of relationships among topics.

The DDC organizes knowledge by disciplines or fields of study. At the broadest level, the DDC is divided into ten main classes, which together cover the entire world of knowledge. Each main class is further divided into ten divisions, and each division into ten sections (not all the numbers for the divisions and sections have been used).

The main structure of the DDC is presented in three summaries (outlines) of the Dewey Decimal Classification. The summaries give Dewey numbers and their accompanying captions. The captions have been edited to make browsing easier, and so may not match the complete heading found in the DDC classification schedules.

The first summary contains the ten main classes, providing a broad overview of the DDC:

Class Caption
000 Computer science, information & general works
100 Philosophy & psychology
200 Religion
300 Social sciences
400 Language
500 Science
600 Technology
700 Arts & recreation
800 Literature
900 History & geography

The first digit in each three-digit number represents the main class. For example, 600 represents technology.

The second summary contains the hundred divisions, ten for each main class. The second digit in each three-digit number indicates the division. For example, 600 is used for general works on technology, 610 for medicine and health, 620 for engineering, 630 for agriculture.

The third summary contains the thousand sections. The third digit in each three-digit number indicates the section. Thus, 610 is used for general works on medicine and health, 611 for human anatomy, 612 for human physiology, 613 for personal health and safety.

The three summaries provide an overview of the intellectual and notational structure of the DDC system, but they do not always reveal the full substance of what the numbers represent. To understand the breadth of each number and caption, one must consult the DDC classification schedules. A variety of educational resources also are available, including an animated Flash introduction to the DDC.

More Information

The Dewey web site contains up-to-date information about the DDC, DDC products and services, and DDC licensing. For more information about the structure and application of the Dewey Decimal Classification, consult the introduction in volume 1 of DDC 22. The introduction is also available online (PDF:191K/37pp.) and in WebDewey. A more in-depth introduction to the Dewey Decimal Classification may be found in Dewey Decimal Classification: Principles and Application, 3d ed., by Lois Mai Chan and Joan S. Mitchell (Dublin, Ohio: OCLC, 2003).

ResearchWorks provides access to the DDC Summaries in two ways:

  • in Microsoft Excel format
  • as a PDF document with additional descriptive text

Please note that your use of the DDC Summaries is governed by Terms and Conditions in addition to the ResearchWorks license.


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