Colon classification (CC) is a system of library classification developed by S. R. Ranganathan. It was the first ever faceted (or analytico-synthetic) classification. The first edition was published in 1933. Since then six more editions have been published. It is especially used in libraries in India.

Its name "colon classification" comes from the use of colons to separate facets in class numbers. However, many other classification schemes, some of which are completely unrelated, also use colons and other punctuation in various functions.

In CC, facets describe "personality" (the most specific subject), matter, energy, space, and time (PMEST). These facets are generally associated with every item in a library, and so form a reasonably universal sorting system.^[1]

As an example, the subject "research in the cure of tuberculosis of lungs by x-ray conducted in India in 1950" would be categorized as:

Medicine,Lungs;Tuberculosis:Treatment;X-ray:Research.India'1950

This is summarized in a specific call number:

L,45;421:6;253:f.44'N5

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Asheesh Kamal