Subject cataloguing - Meaning and Purpose 

Since an entry in the catalogue serves as a document substitute, it is necessary to provide relevant information for individualising it so that the document can be retrieved or located from amongst the others belonging to the same subject category. This job is usually accomplished with the help of a  call number  assigned to the document. In addition to entries for individual documents, the catalogue also contains directions which refer the searcher from one heading to another heading under which potentially relevant information in the form of document entries can be found. Such entries in the catalogue are known as references. These references also help the searcher in locating information about the related subjects to the subjects of his interest. 

"The assigning of headings and references, with retrieval of documents through the medium of a catalogue, in response to request for information on specific subjects is generally defined as subject cataloguing". Subject cataloguing forms an integral part of the total process. Therefore, there is little need to emphasise on the important role of subject cataloguing in libraries. The potential use of library materials cannot be exploited without it, especially in large libraries.  Also, the vast increase in the number of documents in every sphere of human activity, clubbed with the increased complexity of the pattern of knowledge, calls for a foolproof method of access to records on any subject. Thus, subject cataloguing is concerned with subject description of documents.