Main classes

About DDC main classes and summaries

The 10 main classes provide a top-level outline of the DDC. Each main class represents one of the major areas into which the DDC divides recorded knowledge. The numbers and captions of the main classes comprise the first summary of the classification system.
The DDC defines 10 divisions within each main class. The numbers and captions of the main classes and their divisions comprise the 100 divisions of the second summary.
Within each division, the DDC defines sections. The numbers and captions of the main classes, the divisions, and the sections comprise the 1,000 sections of the third summary.

Explore class relationships by moving from a generally relevant class to an appropriately specific subclass.
When classifying, avoid moving too quickly to a narrowly focused search for an appropriate class number. Traversing the DDC hierarchy from the top down helps you remain aware of the broader context of a subject as represented in the DDC.
Get an overview of the structure of the DDC and/or of a particular class, division, or section.

To	Do this
View divisions within a main class	In the Main Classes area, click the hyperlinked caption for the class whose divisions you want to view.
View record for another division or section	In the hierarchy display at the top of a record, click the hyperlinked caption for the division or section you want.
Return to Main Classes screen from record	In the hierarchy display at the top of a record, click the hyperlinked caption DDC, or click Dewey Decimal Classification in the header element.
View Tables screen	At the bottom of the Dewey Linked Data homepage, click Tables. Note: You must be signed in to see the Tables module.