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Call Numbers: Dewey Decimal

Learn how books are organized and labeled at Northwestern University Library

About Dewey Decimal Call Numbers

The Dewey Decimal classification system groups together books on similar subjects by means of their call numbers.There are 10 main Dewy Decimal call number classifications or classes.

Reading a Dewey Decimal Call Number

305.20973 T39  

300   Social Sciences, Sociology & Anthropology

305  Groups of people

305.2  Age

305.20973   In America (0973 at the end means history and description about America)

T39   Taylor

305.20973 T39   The next America : boomers, millennials, and the looming generational showdown / Paul Taylor.

  • Books are arranged sequentially. The first number of a Dewey Decimal call number indicates the general class the call number falls within. In our example, the book is located under the 300s, which is where books on social sciences are classed. If there is a second or third numbers, these indicates a specific divisons and sections. 305 indicates groups of people.
  • Numbers following the first 3 numbers. The numbers define the subject of the book. The number .2 is referring to a book about a specific age group and 0973 means the history and description about America.
  • The Cutter Number is the next set of numbers. The Cutter Number indicates the author or title of the book. It is taken from a table matching names or titles to a set of numbers. In our example, .T39 reflects the first word of the author, Taylor.