Preparing for Academic Writing & Speaking

Doing the research

The Dewey Decimal System

Every book in the library has a call number (or class number) which helps you to find it. The call number identifies each individual book and will be found on the spine of the book. It also indicates the position of a book on a shelf. The most common system of numbering the books in the UK is the Dewey Decimal system.

In this system, books in the same subject area will be shelved together. Call numbers usually consist of numbers and letters. The number represents the subject of the book and the letters usually represent the author.

For example, in the University of Hertfordshire library:

Academic writing course by R. R. Jordan is 428.24 JOR

Study listening by Tony Lynch is 428.4207 LYN

The Dewey Decimal system classifies books as follows:

000-099 General works (including libraries, journalism, general encyclopedias, etc.)

100-199 Philosophy and Related Disciplines

200-299 Religion

300-399 Social Sciences

400-499 Language

500-599 Natural Science and Mathematics

600-699 Technology (Applied Science)

700-799 Arts

800-899 Literature

900-999 General Geography and History

Exercise 1

Each of these classes can be divided into ten smaller classes. For example:

500 Natural Science

510 Mathematics

520 Astronomy & allied sciences

530 Physics

540 Chemistry & allied sciences

550 Science of Earth and other worlds; Geology

560 Palaeontology; Fossils

570 Life sciences; Biology

580 Botany

590 Zoology


Each of these classes may be divided further, for example:

500 Science

590 Zoology

591 Animals - habits and behaviour

592 Invertebrates - animals without backbones

593 Sponges, corals, jellyfish etc.

594 Molluscs - snails, shell-fish, sea-shells

595 Other invertebrates - worms, crabs, spiders

596 Vertebrates - sea squirts and sea grapes

597 Fishes

598 Reptiles and birds

599 Mammals

Even more subdivisions can follow, represented by decimal points. The number of digits will depend on how specific the topic of the book is. For example:

500 Natural Science

590 Zoological Sciences

595 Other invertebrates

595.7 Insects

595.78 Lepidoptera

595.789 Butterflies

So we see that Butterflies (595.789) is a subdivision of Lepidoptera (595.78) which is a subdivision of Insects (595.7). This in turn is a subdivision of Other Invertebrates (595) which is a subdivision of Zoological Sciences (590-599).


The second part of the call number may consist of the initial letters of the author's surname. For example:

595.789 BRU is Butterflies by Beth Wagner Brust

595.789 EHL is Waiting for wings by Lois Ehlert

595.789 FIS is Life of the Butterfly by Heiderose & Andreas Fischer-Nagel

595.789 GIB is Monarch Butterfly by Gail Gibbons

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