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Dewey Decimal Classification (DDC)

January 14, 2026

 

Dewey Decimal Classification (DDC)



The Dewey Decimal Classification (DDC), often referred to as the Dewey Decimal System, is one of the most enduring and widely used library classification systems in the world. It provides a structured way to organize books and other library materials based on subject matter in a systematic and logical manner, making it easier for users to locate resources in libraries. DDC arranges knowledge into ten main classes, each represented by a three-digit number. These classes are further divided into more specific topics using decimal notation. The Dewey Decimal Classification (DDC) is a proprietary library classification system developed by Melvil Dewey. It was first published in the United States in 1876. It is used in approximately 200,000 libraries in over 135 countries.



Contents:

  • History and Development
  • Purpose of DDC
  • Objectives of DDC
  • Structure and Notation of Dewey Decimal Classification
    • The Ten Main Classes of DDC
    • Divisions and Sections of DDC
    • Hierarchical Structure and Decimal Expansion of DDC
    • Notational Hierarchy
    • Decimal Notation and Its Importance in DDC
    • Decimal Notation and Call Numbers
    • Relative Index and Schedules
      • Schedules
      • Relative Index
      • Tables
  • How the DDC Works in Practice
    • Examples of DDC Classifications 
  • Advantages, Benefits, and Global Usage of DDC
  • Limitations of DDC
  • Conclusion
  • DDC Timeline



HISTORY AND DEVELOPMENT

The DDC was conceived by Melvil Dewey, an American librarian, in 1873 while he was a student at Amherst College. The first edition was published anonymously in 1876 as a 44-page pamphlet titled "A Classification and Subject Index for Cataloguing and Arranging the Books and Pamphlets of a Library." Dewey's innovative system was revolutionary because it used decimal numbers to categorize knowledge hierarchically, allowing for infinite expansion as new subjects emerged. 

Over the years, the DDC has evolved significantly. It has gone through 23 major editions, with the most recent print edition released in 2011. Today, it is maintained by OCLC (Online Computer Library Center), a nonprofit cooperative that serves libraries globally. An online version called WebDewey is continuously updated to reflect changes in knowledge and terminology. 


History of Dewey Decimal Classification (DDC)



PURPOSE OF DDC

The primary purpose of the DDC is to organize library materials in a systematic and accessible way. By assigning a unique numerical classification to each item, libraries can ensure that books on similar subjects are shelved together, making it easier for patrons to browse and locate information. This logical arrangement enhances the discoverability of resources and optimizes the efficiency of library operations.



OBJECTIVES OF DDC

The main objectives of the Dewey Decimal Classification are:

  • To organize knowledge logically
  • To facilitate the easy retrieval of information
  • To allow infinite expansion using decimal notation
  • To provide uniformity and consistency in library arrangement



STRUCTURE AND NOTATION OF DEWEY DECIMAL CLASSIFICATION 

At its core, the DDC organizes knowledge into ten main classes, each representing a broad discipline or field of study. These classes are divided into divisions and sections, using a decimal-based notation for increasing specificity. This hierarchical structure allows for precise classification while accommodating growth in any subject area.

DDC is based on a hierarchical structure:

  • Main Classes (000–900)
  • Divisions (10 divisions within each class)
  • Sections (10 sections within each division)

Each level adds greater subject specificity.

The Ten Main Classes of DDC

The DDC categorizes all knowledge into ten main classes, each represented by a three-digit number. These main classes cover a broad spectrum of subjects, from philosophy and religion to science, technology, and history.

Here are the ten main classes:

000 (000–099) - Computer Science, Information & General Works: This class includes encyclopedias, bibliographies, computer science, and journalism.

Example: 004.6 - Local Area Networks (LAN)

100 (100–199) - Philosophy & Psychology: This covers metaphysics, epistemology, ethics, logic, and various schools of psychology.

Example: 150 - Psychology

200 (200–299) - Religion: This class encompasses world religions, mythology, and theology, with a strong focus on Christianity.

Example: 294.3 - Buddhism

300 (300–399) - Social Sciences: This includes sociology, economics, law, political science, education, and social welfare.

Example: 330 - Economics

400 (400–499) - Language: This covers linguistics, specific languages, dictionaries, and grammar.

Example: 420 - English Language

500 (500–599) - Science: This class includes mathematics, astronomy, physics, chemistry, biology, geology, and botany.

Example: 570 - Biology

600 (600–699) - Technology: This covers applied sciences, medicine, engineering, agriculture, home economics, and manufacturing.

Example: 610 - Medicine & Health

700 (700–799) - Arts & Recreation: This includes fine arts, music, performing arts, sports, and recreation.

Example: 796.357 - Baseball

800 (800–899) - Literature: This class covers literature of specific languages, poetry, drama, fiction, essays, and rhetoric.

Example: 823 - English Fiction

900 (900–999) - History & Geography: This includes geography, travel, biography, and history of specific regions and periods.

Example: 940 - History of Europe

Divisions and Sections of DDC

Each main class is further subdivided. For instance, the 500s (Natural sciences and mathematics) break down into divisions like 510 (Mathematics), 520 (Astronomy), and so on. These divisions are then segmented into sections, such as 595 (Other invertebrates) within the 590s (Zoological sciences).

Divisions and Sections: Examples

Example 1: Science (500)

  • 500 – Natural Sciences
  • 510 – Mathematics
  • 516 – Geometry
  • 516.3 – Analytic Geometry

Example 2: Technology (600)

  • 600 – Technology
  • 630 – Agriculture
  • 636 – Animal Husbandry
  • 636.7 – Dogs

Example 3: Literature (800)

  • 800 – Literature
  • 820 – English Literature
  • 823 – English Fiction
  • 823.914 – Contemporary English Fiction

Hierarchical Structure and Decimal Expansion of DDC

Within each main class, the DDC uses a hierarchical structure, expanding on subjects through the use of decimal points. This allows for increasingly specific categorization. Each three-digit number can be further subdivided by adding a decimal point and more digits.

For instance, consider the 600 – Technology class.

  • 610 – Medicine & Health (a division of Technology)
  • 612 – Human Physiology (a subdivision of Medicine)
  • 612.8 – Nervous System (a subdivision of Human Physiology)
  • 612.82 – Brain (a further subdivision of the Nervous System)

This decimal expansion allows for immense specificity, ensuring that even very niche topics have a unique and logical place within the system.

Notational Hierarchy

In DDC, longer numbers represent more specific subjects, while shorter numbers indicate broader topics.

Example:

  • 600 – Technology
  • 620 – Engineering
  • 621 – Applied Physics
  • 621.381 – Electronics

Decimal Notation and Its Importance in DDC

One of the most powerful features of DDC is decimal notation, which allows:

  • Unlimited subject expansion
  • Precise classification of documents
  • Easy addition of new topics without disturbing existing numbers

Example:

  • 300 – Social Sciences
  • 320 – Political Science
  • 320.54 – Nationalism
  • 320.540954 – Nationalism in India

Decimal Notation and Call Numbers

The DDC uses a decimal system for refinement. A call number might look like 595.789, where:500 represents Natural sciences.

  • 590 narrows to Zoological sciences.
  • 595 specifies Other invertebrates.
  • 595.7 focuses on Insects.
  • 595.78 targets Lepidoptera (moths and butterflies).
  • 595.789 pinpoints Butterflies specifically.

To distinguish between books on the same topic, the author's last name (or title if no author) is added, often abbreviated to the first three letters, e.g., 595.789/BRO for a book by James P. Brock. 

Books are shelved in numerical order, treating the numbers as decimals. For example:

  • 331 comes before 331.01.
  • 331.0413 follows 331.041 but precedes 331.042.

This ensures precise ordering, even with varying lengths of numbers.

Relative Index and Schedules

The DDC is comprised of several key components:

Schedules: These are the heart of the DDC, listing the classification numbers and their corresponding subjects in a systematic order.

Relative Index: The Relative Index is an alphabetical list of subjects with corresponding DDC numbers. This alphabetical index provides terms and concepts, directing users to the appropriate DDC numbers regardless of where they appear in the schedules. It helps overcome the challenge of knowing where a subject might fit into the ten main classes. For example, "Child Psychology" might be found under Psychology (155.4) or Social Sciences (305.23). The Relative Index guides you to all relevant numbers.

The Relative Index in DDC helps users:

  • Find the correct class number quickly
  • Locate subjects that may appear in more than one discipline

Example:
  • Economics – 330
  • Buddhism – 294.3
  • Climate Change – 363.73874

Tables: These provide standardized numbers that can be added to base numbers to further refine a classification. For example, a table for geographical areas allows you to specify a book about the history of France (944) or the history of a specific city within France.



HOW THE DDC WORKS IN PRACTICE

Libraries assign call numbers to materials, which are typically printed on the spine. Non-fiction books follow the DDC strictly, while fiction is often organized alphabetically by author. Special prefixes like "REF" (Reference) or "BIO" (Biography) may indicate separate sections. 

Examples of DDC Classifications 

Here are some real-world examples to demonstrate the system's application: 

1. A book on tigers: Classified under 599.756. 500: Natural sciences.

  • 590: Zoology.
  • 599: Mammals.
  • 599.7: Carnivores.
  • 599.75: Felidae (cats).
  • 599.756: Tigers specifically 

2. A cookbook on Italian cuisine: 641.5945.600: Technology.

  • 640: Home economics.
  • 641: Food and drink.
  • 641.5: Cooking.
  • 641.59: Cooking by region.
  • 641.594: European cooking.
  • 641.5945: Italian cooking.

3. A biography of Abraham Lincoln: Often in 973.7092 (U.S. history during the Civil War era) or under BIO/LIN, depending on the library's conventions.

  • Biographies may use 920–929 or integrate into historical classes.

4. Computer programming basics: 005.1.

  • 000: Generalities.
  • 005: Computer programming, programs, data.
  • 005.1: Programming fundamentals. 

These examples show how the DDC allows users to browse related topics easily—books on similar subjects are shelved together.



ADVANTAGES, BENEFITS, AND GLOBAL USAGE OF DDC

The DDC's strengths lie in its flexibility and universality. Its decimal structure permits endless subdivisions, adapting to new fields like computer science (added in later editions). It's particularly user-friendly for public and school libraries, where patrons can intuitively navigate from broad to specific topics. However, critics note biases in its original design, such as a Western-centric focus (e.g., more space for Christianity than other religions), though revisions have addressed some issues. Alternatives like the Library of Congress Classification are preferred in academic libraries for greater detail. Today, abridged versions suit smaller libraries, and digital tools like WebDewey enhance cataloging efficiency.

Benefits of DDC:

  • Universality: Its widespread adoption allows for easier sharing of resources and understanding of library collections across different institutions globally.
  • Browsability: The logical grouping of subjects makes it easy for patrons to discover related materials by browsing shelves.
  • Flexibility: The decimal system allows for continuous expansion and adaptation to new fields of knowledge.
  • Simplicity (Relative): While it can appear complex initially, its basic structure of ten main classes is relatively easy to grasp.



LIMITATIONS OF DDC

  • Bias toward Western knowledge
  • Limited hospitality for interdisciplinary subjects
  • Less suitable for very large academic or research libraries



CONCLUSION

The Dewey Decimal Classification remains a cornerstone of library organization, bridging the gap between vast knowledge repositories and curious users. DDC is a remarkably effective and widely used tool for organizing knowledge. Its simplicity, logical structure, and flexibility make it ideal for general libraries. Despite certain limitations, DDC continues to evolve, reflecting changes in knowledge and information organization. Its hierarchical structure, decimal expansion, and comprehensive indexing enable libraries to manage vast collections, making information accessible to millions of users worldwide. It is a testament to Melvil Dewey's foresight and the enduring power of systematic organization.



DDC TIMELINE

Since the publication of its first edition in 1876, the Dewey Decimal Classification (DDC) system has crossed many milestones. Many of these milestones have advanced the organization of library collections to help librarians meet their users' information needs more efficiently.

1876 A Classification and Subject Index for Cataloguing and Arranging Books and Pamphlets of a Library—the first edition of the DDC—is published anonymously in Amherst, Massachusetts.

1885 Second edition of the DDC is published under Melvil Dewey's name.

1900 The first abridged edition of the DDC is published.

1911 The seventh edition of the DDC is published, which is the first to carry the Forest Press imprint.

1916 The Decimal Classification Advisory Committee—the American Library Association's (ALA) first advisory committee—is appointed.

1927 The DDC editorial office moves to the Library of Congress in Washington, DC.

1930 The Library of Congress begins to print Dewey numbers on catalog cards.

1931 Melvil Dewey, creator of the DDC, dies December 26 at age 80.

1937 The Decimal Classification Committee, a forerunner to the present-day Dewey Decimal Classification Editorial Policy Committee, is established.

1953 The Dewey Decimal Classification Editorial Policy Committee is reconstituted to represent the American Library Association, Forest Press and the Library of Congress to guide to editorial development of the DDC.

1958 The 16th edition of the DDC is published, which is the first to be edited under an agreement between the Library of Congress and Forest Press.

1988 Forest Press, based in Albany, New York, becomes a division of OCLC.

1993 OCLC Forest Press publishes Electronic Dewey, the first library classification scheme in electronic form.

1996 The 21st edition of the DDC and Dewey for Windows® are published, which is the first time print and electronic formats are published simultaneously.

1999 The OCLC Forest Press office moves from Albany, New York, to OCLC headquarters in Dublin, Ohio; three years later, the Forest Press imprint is retired.

2000 WebDewey in CORC is published.

2002 WebDewey and Abridged WebDewey are published.

2003 The 22nd edition of the DDC is published.

2004 The 14th edition of the Abridged DDC is published.

2005 The German edition of DDC 22 is published.

2007 EDUG (European DDC Users Group) was established.

2009 The Italian edition of DDC 22 is published.

2011 WebDewey 2.0 is released.

2011 The 23rd Edition of the DDC is published.

2011 Swedish WebDewey is released.

2012 The 15th Abridged Edition of the of the DDC is published.

2012 Electre Guide (a French abridgement) of DDC 23 is published.

2012 German WebDewey is released.

2013 The Vietnamese edition of DDC 23 is published.

2014 Italian WebDewey is released.

2015 The French edition of DDC 23 is published.

2015 Norwegian WebDewey is released.

2015 French WebDewey is released.

2017 The Spanish edition of DDC 22 is published.

2018 OCLC introduces Dewey print-on-demand (a print copy of the DDC).

2024 OCLC releases Dewey linked data.





CITATION INFORMATION

Article Title
  • Dewey Decimal Classification (DDC)
Author
  • Salman Haider
Website Name
  • Librarianship Studies & Information Technology
URL
  • https://www.librarianshipstudies.com/2026/01/dewey-decimal-classification-ddc.html



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