Dewey Decimal System Day

What the day is

Dewey Decimal System Day is observed on December 10, the birthday of Melvil Dewey, who was born in 1851. It marks the classification system that bears his name, which sorts library books by subject so that readers can find them on the shelf. Librarians and library fans sometimes use the day to talk up how their collections are arranged.

If you have ever walked down a library aisle and found a row of books on cooking, dogs or history in a predictable place, you have used the system, whether you knew it or not.

Origin and background

Dewey first published the system in 1876 as a short pamphlet. It divides all knowledge into ten main classes numbered from 000 to 900, such as 500 for natural sciences and mathematics, 600 for technology and 900 for history and geography. Each class divides into ten divisions, which divide again, and decimal points allow ever finer subjects. It has been revised many times and is now maintained by OCLC, a library cooperative in Ohio, which also owns the trademark.

The system is not without critics. Its structure reflects the assumptions of the late nineteenth century. For example, most of the numbers in the religion class go to Christianity. Dewey himself was a controversial figure, and his conduct and views drew criticism during his lifetime. Libraries have adapted the scheme in response, and many research libraries use the Library of Congress Classification instead, which uses letters and numbers.

Even so, Dewey remains the most widely used system in the world, particularly in school and public libraries, because it is easy to learn and flexible enough to grow.

How to take part

• Visit your local library and find where a favorite subject lives by its number.
• Browse an unfamiliar number range, such as 398 for folklore or 641 for cooking, and check out a book you would not usually pick.
• Ask a librarian how the library decides where a new book goes.
• Try arranging a small shelf at home by subject, and see how many categories you need.
• Thank a librarian, and consider donating a book or joining the Friends of the Library.