How to Learn the Dewey Decimal System

The Dewey Decimal System can be used to locate a book on any subject.
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The Dewey Decimal System, created by Melvil Dewey, is used in more than 200,000 libraries around the world. Learning the Dewey Decimal System will allow you to locate a book on any subject. The system uses 10 main classifications to divide books into broad categories and divides those into 10 more specific subcategories. The books are then further divided and categorized into specific subjects and topics, each being assigned a so-called call number; the more specific the category, the longer the call number.

    Find the Dewey Decimal System chart at your library; it's usually near the card catalog.

    Locate the main category, three-digit number section of your target subject. The main Dewey decimal categories are Generalities under 000 (those not categorized elsewhere); Philosophy and Psychology are 100; Religion falls under 200; Social Sciences are 300; Language 400; Natural Science and Mathematics are 500; Technology and Applied Sciences fall under 600; Arts, 700; Literature is 800; and Geography and History fall under 900. A book on butterflies would be filed under main classification 500, which is for natural science and mathematics.

    Determine the subcategory for the type or group of your subject. For the Natural Science and Mathematics 500 main classification, a book on algebra would be sub-categorized under 512; chemistry under 540; botany under 581; and butterflies would be found under zoological sciences, 590.

    Find the specific subject by looking for the call number in the card catalog. A book on intermediate algebra would have a call number of 512.9 and butterflies, 595.789.

    Write the number down and locate the book on the shelves by following the numbers on the spines of the books up to the call number of your book.


    • Check with a librarian to see if the library’s card catalog is available on computer, which will simplify the process.

      You can also find a specific book by doing a search by title or author to find the Dewey Decimal call number.

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