In the Library, we use the Dewey Decimal system to arrange and classify our library collections.
Dewey is a numerical system which groups a library’s material into the following ten main areas of knowledge:
000 - Computer science, information & general works
100 - Philosophy & psychology
200 - Religion
300 - Social sciences
400 - Language
500 - Science
600 - Technology
700 - Arts & recreation
800 - Literature
900 - History & geography
Each of these ten areas are further divided to create more specific subject numbers. This is done by adding numbers after the decimal point. You can see an example of this in a section of the 500s below:
551 - Geology, hydrology, meteorology
551.01 – Philosophy and theory of geology
551.1 – Gross structure and properties of the earth
551.21 – Volcanoes
551.22 – Earthquakes
551.23 – Thermal waters and gases
551.5 – Meteorology
Every item in the library has a shelf mark, which consists of a Dewey number and filling letters (normally the first letters of the author’s surname). Items are arranged firstly by Dewey number and then alphabetically by filling letters (see diagram below). The number sequence flows on the shelves from left to right.

When looking for a print book that has numbers after the decimal point, it’s important to remember that after the decimal point the numbers are filing digit by digit, not by the whole number. For example in the diagram above, 551.21 is found on the shelf before 551.5 as it is a 2 then 1, not 21 and is therefore lower than 5.
You can find out the shelf mark and availability of a book in library search. Library Search is a powerful search engine that you can use to find and access high quality academic resources. For more information, please see the following guide: ‘Library Search Help’.
