In the Dewey Decimal System, each number stands for a special topic or subject.
Every book or item in a library is given a number and is put on the shelf in number order.
Books with the same number which are about the same topic/subject are grouped together on the library shelves.
Here are three tables for the Dewey Decimal System.
1. In the first, Dewey divided knowledge into 10 main subject areas like this:
100 Philosophy and Psychology
300 Social Science
500 Natural Science and Mathematics
600 Technology (Applied Sciences)
900 Geography and History
2. In the second table Dewey divided each of the 100s into 10s like this example using the 500s
550 Earth Sciences
570 Life Sciences
580 Botanical Sciences
590 Zoological Sciences
Then Dewey did it again!
3. In the third, Dewey divided each of the numbers again into 10 smaller numbers. Each time he was making the subjects/topics more and more specific.
Here's how Dewey divided the 590s which are all about animals
590 Animals for books with general information about lots of animals
591 Natural history of animals
592 Invertebrates: animals without a backbone such as worms
593 Marine and seashore invertebrates such as corals
594 Molluscs such as animals with shells: snails and octopus
595 Arthropods such as insects, spiders and centipedes
597 Cold blooded vertebrates such as reptiles and fish, frogs and toads
599 Mammals of land and ocean