The Dewey Decimal Classification (DDC) sorts all knowledge into ten main classes, each split into ten, and again into ten — giving every book a number that places it beside related books. It’s why the cookery books sit together, and the history books down the next aisle.

Dewey’s quiet genius is that you can browse a library shelf and discover — find the book you wanted, then notice three better ones right beside it. That happy accident isn’t luck; it’s a 19th-century numbering idea still doing its job in libraries worldwide.

How the numbers stack up

  • Ten main classes — 000 general, 100 philosophy, 200 religion, 300 social sciences, 400 language, 500 science, 600 technology, 700 arts, 800 literature, 900 history & geography.
  • Each splits into ten — 500 science → 510 mathematics, 520 astronomy, 530 physics…
  • Decimals go finer still — 516 geometry, 516.3 analytic geometry. The more precise the topic, the longer the number.
Reading a Dewey number
A book on African elephants might sit at 599.67. The 500 says science, 590 zoology, 599 mammals, and the decimals narrow it to elephants. Walk to that number and you’re among all the mammal books — the system shelved your topic next to its relatives, automatically.

Strengths and limits

Dewey is wonderfully browsable and works well for general and public libraries. Its limits show with very large or highly specialised collections, where numbers grow unwieldy — which is exactly where the next scheme tends to take over.

Try this
Guess the main Dewey class (000–900) for three books you own. Then think: does each sit comfortably in one class, or does it straddle two? That tension is the everyday puzzle of classification.

🔗 A friendly free guide: OCLC — Dewey Decimal Classification

For big research and academic libraries, a different system gives more room to breathe. On to Library of Congress Classification.

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Última modificación: viernes, 5 de junio de 2026, 08:07