Colon Classification, system of library organization developed by the Indian librarian S.R. Ranganathan in 1933. It is general rather than specific in nature, and it can create complex or new categories through the use of facets, or colons. The category of dental surgery, for example, symbolized as L 214:4:7, is created by combining the letter L for medicine, the number 214 for teeth, the number 4 for diseases, and the number 7 for surgery. In Colon Classification, there are 108 main classes (previously there were 33) and 10 generalized classes (broadly divided between the humanities and sciences), which are represented by a mixed notation of Arabic numerals and roman and Greek letters. This book explains the decimal classification and colon classification in perspectives. This book will bring new insights in the field of decimal classification and colon classification.