December 10 is Dewey Decimal System Day

Dewey Decimal Classification (DDC), commonly known as the Dewey Decimal System, was established in the US by Melvil Dewey [born December 10, 1851] in 1876 as a system to shelve books [mostly non-fiction] in a library based on subject. It was originally described in a 44-page pamphlet, but is now expanded to multiple volumes with the latest edition published in 2012. It is used in 200,000 libraries in 135 countries.

https://en.wikipedia.org/wiki/Dewey_Decimal_Classification

000 – Computer science, information and general works
100 – Philosophy and psychology
200 – Religion
300 – Social sciences
400 – Language
500 – Pure Science
600 – Technology
700 – Arts and recreation
800 – Literature
900 – History and geography

Each class has 10 divisions which are then further categorized into 10 sections.

Here are ALL the sections
https://www.oclc.org/content/dam/oclc/dewey/resources/summaries/deweysummaries.pdf

Other classification systems are the Library of Congress system and the Universal Decimal Classification system, which allow for greater detail and are used in academic and similar settings.

https://en.wikipedia.org/wiki/Library_of_Congress_Classification

https://en.wikipedia.org/wiki/Universal_Decimal_Classification

Chart comparing Dewey and Library of Congress systems
https://en.wikipedia.org/wiki/Comparison_of_Dewey_and_Library_of_Congress_subject_classification

https://nationaltoday.com/dewey-decimal-system-day/