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Dewey Decimal Classification

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Dewey Decimal Classification

The Dewey Decimal Classification (DDC) system is a general knowledge organization tool that is continuously revised to keep pace with knowledge. The system was conceived by Melvil Dewey in 1873 and first published in 1876. The DDC is the most widely used classification system in the world. Libraries in more than 135 countries use the DDC to organize and provide access to their collections, and DDC numbers are featured in the national bibliographies of more than 60 countries. One of Dewey’s great strengths is that the system is developed and maintained in a national bibliographic agency, the Library of Congress. The Dewey editorial office is located in the Decimal Classification Division of the Library of Congress, where classification specialists annually assign over 110,000 DDC numbers to records for works cataloged by the Library[1].

Organizational Structure

In the DDC, basic classes are organized 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). Arabic numerals are used to represent each class in the DDC. A decimal point follows the third digit in a class number, after which division by ten continues to the specific degree of classification needed.

Notational hierarchy is expressed by length of notation. Numbers at any given level are usually subordinate to a class whose notation is one digit shorter; coordinate with a class whose notation has the same number of significant digits;and superordinate to a class with numbers one or more digits longer. The underlined digits in the following example demonstrate this notational hierarchy:

  • 600 Technology
  • 630 Agriculture and related technologies
  • 636 Animal husbandry
  • 636.7 Dogs
  • 636.8 Cats
“Dogs” and “Cats” are more specific than (i.e., are subordinate to) “Animal husbandry”; they are equally specific as (i.e., are coordinate with) each other; and “Animal husbandry” is less specific than (i.e., is superordinate to) “Dogs” and “Cats”[2].

Broadest Classification

  • 000 Generalities
  • 100 Philosophy & psychology
  • 200 Religion
  • 300 Social sciences
  • 400 Language
  • 500 Natural sciences & mathematics
  • 600 Technology (Applied sciences)
  • 700 The arts
  • 800 Literature & rhetoric
  • 900 Geography & history

Further Reading