How to use the Dewey Decimal System

Along with 95% of public libraries in the United States, the Hershey Public Library organizes its collection according to the Dewey Decimal System. Once you understand the structure of the system, it's easy to find specific materials as well as topics for browsing.

Created by Melville Dewey and released in 1876, the Dewey System divides non-fiction works in to ten general categories using numbers that range from 000-999. Each number at the 100 level represents a new category; within these categories, topics are divided into subcategories at the 10 level, and further divided at the 1 level. At this point, decimal points are used for categorization. This use of decimal points allows the system to expand as needed into new areas of information.

Once in these categories, books are filed by the first three letters of the author's last name:

Top Level

Sub category

Sub-sub category

Decimal Level

300 - Social Sciences
  320 - Political Science    
    323 - Civil and Political Rights  

323.4 - Specific Civil

Rights, limitation and suspension of civil rights


NOTE: The Dewey Decimal System applies to Non-Fiction works excluding Biography.

The table below lists the general Dewey Categories:




General (includes computer, software, book collecting)


Philosophy and Psychology (includes metaphysics, logic, self-help, cognition and unexplained phenomena)




Social Sciences (incudes politics, current events, crime, economics)


Language (includes English grammar, foreign languages)


Natural Sciences and Mathematics


Technology (Applied Sciences) (includes medicine, health, diet and fitness, cooking, childcare, parenting)


Arts (includes music, painting, sports and recreation)


Literature and Rhetoric (includes plays, poetry, literary criticism - but NO NOVELS)


Geography and History (includes travel guides, world and US history)

For a complete list of Dewey categories, visit this site:

Additional information