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Dewey Decimal System

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Ideas | March 17, 2012

Books and movies intended to give facts, or accounts of real things and events are called nonfiction. All Cambridge Libraries locations and most public libraries organize their nonfiction collections in the same way, using the Dewey Decimal System. Every nonfiction book, movie or sound recording is given a unique number using the Dewey Decimal classification system.

The Dewey Decimal numbers appear on the sides of nonfiction books and DVDs. They are called "call numbers". The books are then put on the shelves in order by the Dewey number. Here are some examples of Dewey Decimal call numbers:

  • 158 (self help)
  • 364.1 (true crime)
  • 636.7 (pet dogs)
  • 629.2872 (car repair)
  • 641.5946 (Spanish cooking) 
  • 649.1 (parenting)
  • 745 (crafts)
  • 940.3 (World War 1)

What do the numbers mean?

The  Dewey Decimal System organizes all knowledge into subject categories.  Here are the ten main classes, or subject areas:

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

Each class is subdivided further. Here is how science is subdivided:

500 Science
510 Mathematics
520 Astronomy
530 Physics
540 Chemistry
550 Earth sciences & geology
560 Fossils & prehistoric life
570 Life sciences; biology
580 Plants (Botany)
590 Animals (Zoology)

Each of the numbers above are subdivided even further (501, 502, etc). Call numbers often have decimal places that lets books and movies be categorized into even more precise groups.


It seems so complicated! How do I find what I want?

Using the library isn't about about memorizing subjects, categories and subcategories.

Use the library catalogue or ask a librarian to help you find where books, movies or music that interest you are located. If you like to cook, you'll find that books about cooking are given the Dewey number 641.  If you are doing home renovations, you'll find help in the 643.7 section. Doing a big  home construction project? Look in the Dewey numbers ranging 690-698.

When you know the Dewey number of your topic, you can go straight to that number at any public library in Cambridge and browse the shelves to find more on your subject.

Want to know more? Here are links to more information:

Quick guide to the Dewey Decimal System at Idea Exchange

Detailed guide to Dewey Decimal system

Presentation on how the Dewey system works