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How to Read a Dewey Number

Where to Find a Call Number in the Library
Summary of the Dewey Decimal Numbers

Step 1The Dewey Decimal System takes the entire world of knowledge and breaks it down into ten major categories. The "hundreds" (000 - 900) are used to represent this first level:

000 Generalities
100 Philosophy & psychology
200 Religion
300 Social Science
400 Language
500 Natural sciences & mathematics
600 Technology (Applied sciences)
700 The Arts   Fine and decorative arts
800 Literature
900 Geography & History

Step 2Each major category is then broken down into nine sub-categories. The "tens" (10 - 90) are used to represent the second level:

600 Technology (Applied sciences)
610 Medical Sciences   Medicine
620 Engineering and allied operations
630 Agriculture and related technologies
640 Home economics and family living
650 Management and auxiliary services
660 Chemical engineering and related technologies
670 Manufacturing
680 Manufacture of products for specific uses
690 Building

Step 3The sub-categories are then broken into even more specific topics. The "ones" (1 - 9) are used to represent this third level:

630 Agriculture and related technologies
631 Specific techniques; apparatus, equipment, materials
632 Plant injuries, diseases, pests
633 Field and plantation crops
634 Orchards, fruits, forestry
635 Garden crops (Horticulture)   Vegetables
636 Animal husbandry
637 Processing dairy and related products
638 Insect culture
639 Hunting, fishing, conservation, related technologies

Step 4The final break-down to the most specific topics is created by adding decimals to the existing number. The more numerals after the decimal point, the more focused the topic.

633 Field and plantation crops
633.1 Cereal grains (Cereals)
633.2 Forage crops
633.3 Legumes, other forage crops
  633.31 Alfalfa
  633.32 Trifolium clovers
  633.33 Cowpeas
  633.34 Soybeans
  633.35 Vetches

The Dewey Decimal Classification is copyright 1996-2000 OCLC Online Computer Library Center, Incorporated.
DDC, Dewey Decimal Classification, and Dewey are registered trademarks of OCLC Online Computer Library Center, Inc.
Used with Permission.

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Last Update: 16 August 2001
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