In an analytico-synthetic classification, subjects are divided into facets (aspects), and class numbers are synthesised from the classifications. Analytico-synthetic method is much more powerful than more traditional schemes such as the Library of Congress classification or Dewey Decimal Classification, but can result in much longer class numbers. It has been a major theoretical influence to classification researchers.
Its name "colon classification" comes from the use of colons to separate facets in class numbers. It is especially used in libraries in India.
As an example, the subject "research in the cure of tuberculosis of lungs by x-ray conducted in India in 1950" results in a call number