The Dewey Decimal Classification System

The Dewey Decimal Classification (DDC) is a system for arranging items in a library.  It is the most widely used system and is the one often used by most public libraries and some small academic libraries.  This system divides materials into ten main groups using a combination of numbers.   These ten main groups are divided into specific fields.   When a field needs to become even more specific, decimals are use to represent these specific areas.  


Main Dewey Decimal Classification groups

000-099   Generalities (encyclopedias, bibliographies, periodicals, journalism)

100-199   Philosophy and related disciplines (psychology, logic, etc.)

200-299   Religion

300-399   Social sciences (economics, sociology, civics, law, education, vocations, customs)

400-499   Language (language, dictionaries, grammar)

500-599   Pure sciences (mathematics, astronomy, physics, chemistry, geology, biology, zoology)

600-699   Technology and applied sciences (medicine, engineering, agriculture, business, radio)

700-799   The arts (architecture, sculpture, painting, music, photography, recreation)

800-899   Literature (novels, poetry, plays, criticism)

900-999   Geography, history, and related disciplines

For example, class 600-699, Technology and Applied Sciences, is subdivided into ten special classes.   The class 610-619 contains Medical Science/Medicine and is subdivided into classes such as Human Anatomy, Human Physiology, Promotion of Health, Pharmacology, and Experimental Medicine.   Each of these subdivisions is further divided.   For example, materials on Diseases are listed under 616 with materials covering Diabetes being listed under 616.462 and materials covering Heart Disease are listed under 616.12.

Using the Dewey Decimal Classification System

Your local public library probably uses the Dewey Decimal Classification System to organize its materials so it is important to have a general understanding of how this system works. (In addition to the call number, it is important to note which Item Location is indicated in the catalog:   Stacks, Reference, Audiovisual, Special Collections, etc.)

The call number on the spine of an item usually contains two or three lines. Each line should be read separately. A typical call number might read as follows:

(Line 1) 610.736      OR      (Line 1)  610.736
(Line 2) .L61                       (Line 2)  L
(Line 3) 1981       

Line 1.  Materials are shelved by the whole numbers first, then by the numbers following the decimal point. The numbers to the left of the decimal point are whole numbers. Numbers to the right of the decimal point are not and are shelved digit by digit rather than by the entire number. (This is the part of the call number that is confusing to many library users.)  For example, 607.2 is shelved before 607.25 because 607.2 really means 607.20.  Since 607.20 precedes 607.25, it would be shelved first. If you become confused, simply add a "mental" zero to a single digit when comparing it to a double digit.

The call numbers below are in correct order from top to bottom.



Line 2.  The second line usually refers to the author of the item.  Some libraries will list the first few letters of the author's last name on this line.   In these cases, items with the same first line will be shelved in alphabetical order by author's last name.  If there is more than one item with the same first line of the call number and author, then the materials are shelved in order the title of the item. 


Many libraries use the Library of Congress Cutter Tables for this second line. The Cutter is a combination of letters and numbers usually representing the author's last name.  The Cutter is preceded by a decimal point and are read one digit at a time.  

Line 3.  If the call number has three lines, this third line will usually be a four digit number which reflects the date of publication (i.e., 1980, 1986).  If the preceding lines are identical, then the items will be shelved in chronological order by the date of publication.

Additional Resources:

Let's Do Dewey

Middle Tennessee State University (Not for the squeamish!)
Dewey Decimal System Homepage OCLC

Finding materials on the shelf can be confusing at first.  Don't be embarrassed to ask a Librarian for help.  That is why we are here!