Introduction to the Dewey Decimal Classification

What is the Dewey Decimal System?

Classification means identifying and grouping items into classes, organizing knowledge based on shared characteristics, such as by subject. In libraries, classification is used to link the conceptual content of a book (or document) to its physical location on the shelf.

The world's most widely used library classification system is the Dewey Decimal Classification (DDC), created in 1873 by the American librarian Melvil Dewey. It is a tool that undergoes continuous revision to ensure it encompasses all new knowledge. In fact, the DDC is now in its 23rd edition.

Read our tips on How to find your way around the shelves.

On the subject:

Italian Library Association. Introduction to the Dewey Decimal Classification - AIB WEB.
Lois Mai Chan and Joan S. Mitchell. Dewey Decimal Classification: Principles and Application. 3rd ed. Dublin, OH: OCLC, 2003.

Organization and functionality

How the DDC is structured

The Dewey Decimal Classification scheme is organized hierarchically, grouping knowledge into 10 main classes. Each class is divided into 10 divisions, and each division is further divided into 10 sections. This system allows for the addition of new classes or the unlimited expansion of existing ones by introducing new subject areas.

The 10 main classes are:

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

The main functions of the DDC

Cataloging: assigns cataloged resources to the class that corresponds to their subject matter;
Topographic: It allows volumes to be arranged by subject area, which means books covering the same topic can be found on the same shelf, making it easier for users to find what they’re looking for.

Social and Political Science area