OCLCThe Dewey Decimal Classification is the most widely used library classification system in the world, employed by approximately 200,000 libraries in over 135 countries. Its decimal notation system, which uses three-digit base numbers extensible through fractional decimals, has made it the dominant method for organizing general library collections since the late nineteenth century.
Background
Melvil Dewey developed the classification system in 1873 while working at the Amherst College library, publishing the first edition in 1876 as a 44-page pamphlet titled A Classification and Subject Index for Cataloguing and Arranging the Books and Pamphlets of a Library. That first edition contained 2,000 index entries and was printed in 200 copies. The system introduced the revolutionary concept of relative location, where books are shelved in relation to other books on similar topics rather than assigned permanent positions based on acquisition order. This contrasted with the fixed positioning used by most US libraries at the time, where shelf locations were tied to the order of acquisition rather than subject matter.
The second edition (1885) expanded substantially to 314 pages with 10,000 index entries. By 1927, approximately 96% of US public libraries and 89% of college libraries had adopted the system. The Library of Congress began printing DDC numbers on its catalog cards in 1930, further cementing adoption. The Lake Placid Club Educational Foundation managed the classification after Dewey's death in 1931 until OCLC acquired the trademark and copyrights by purchasing Forest Press in 1988.
Purpose and Scope
The DDC organizes library materials by discipline rather than subject, meaning that a topic may appear in more than one class depending on the disciplinary context. The system is designed for general libraries of all sizes, with an abridged edition available for smaller collections of 20,000 titles or fewer. The first abridged edition was published in 1894, and abridged editions have generally paralleled the full editions since.
Key Structure
The classification comprises ten main classes, each divided into ten divisions, each with ten sections, yielding approximately 1,000 base classes:
| Class | Subject Area |
|---|---|
| 000 | Computer science, information and general works |
| 100 | Philosophy and psychology |
| 200 | Religion |
| 300 | Social sciences |
| 400 | Language |
| 500 | Pure science |
| 600 | Technology |
| 700 | Arts and recreation |
| 800 | Literature |
| 900 | History and geography |
Six auxiliary tables allow classifiers to construct compound numbers by combining subject classes with facets for standard subdivisions, geographic areas and historical periods, subdivisions for the arts and literature, subdivisions of individual languages, ethnic and national groups, and languages. This combination of enumeration and faceting makes the system synthetic in nature.
Technical Features
The DDC notation is purely numeric, using Indo-Arabic numbers arranged decimally. The hierarchical structure means that removing rightmost digits produces progressively broader classes (e.g., 516.375 Finsler geometry narrows from 516.37 Metric differential geometries, from 516.3 Analytic geometries, from 516 Geometry). The system also employs mnemonics; for example, the digit 5 consistently represents Italy across different contexts (945 history of Italy, 450 Italian language, 195 Italian philosophy).
A Relative Index provides alphabetical access to the classification, pointing to class numbers rather than page numbers in the schedules. Dewey originally called it the "Relativ Index," reflecting his enthusiasm for spelling reform.
Editions and Versions
Through 23 major editions, the DDC has grown from a 44-page pamphlet to a four-volume work. The 23rd edition, published in mid-2011, is the last printed full edition. The 15th abridged edition appeared in early 2012. In 2017, the editorial staff announced that the English edition would no longer be printed. WebDewey and Abridged WebDewey are updated quarterly and represent the current authoritative version. The first electronic version was created in 1993. An experimental linked data version at dewey.info operated from 2009 to 2015 but is no longer available.
Governance and Maintenance
OCLC maintains the classification with editorial staff based partly at the Library of Congress and partly at OCLC. The Decimal Classification Editorial Policy Committee, a ten-member international board, reviews editorial work and meets twice yearly. Joan Mitchell served as editor for editions 21-23 (until 2013), Michael Panzer became Editor-in-Chief in 2013, and Rebecca Green has served as Dewey Editorial Program Manager since 2016.
Influence and Adaptations
The DDC served as the basis for the Universal Decimal Classification (UDC), developed by Paul Otlet and Henri La Fontaine beginning in 1895. Regional adaptations include the Korean Decimal Classification, the New Classification Scheme for Chinese Libraries, and the Nippon Decimal Classification.
Criticisms
The classification has been criticized for its treatment of religion, where Christianity occupies most of the 200 division while all other religions are compressed into the 290s. The literature section similarly privileges European languages (810-889) over the rest of the world's literatures (890s). The treatment of topics related to women has also been noted for implicit bias, though changes have been made in successive editions. Some US libraries, beginning with Maricopa County Library District in Arizona in 2007-08, have abandoned DDC in favor of the BISAC system used by commercial bookstores.
Related Standards
- Library of Congress Classification (LCC) -- the other major classification system used in US libraries, favored by large academic and research libraries
- Universal Decimal Classification (UDC) -- an analytico-synthetic classification derived from DDC, used internationally for bibliographic services