Thesaurus in Post-Coordinate Indexing Systems 

Thesaurus has come into existence as a tool for vocabulary control in  post-coordinated indexing system. It helps the  indexer in selecting the appropriate terms for indexing, as the indexer may not be familiar with the subject field. It also aids the indexer in his choice of search terms, especially in searching a field with which he is not intimately familiar. 

Besides providing alternative search paths, a thesaurus aids in choosing terms for summation. When information on all the aspects of a subject field is required, search has to be made covering all the related aspects. Here the searcher may not be able to recall all the information that the system can gave without the aid of a thesaurus. In the case of computer  searching, the  links between words used in documents and words used as descriptors in indexing are assembled via a thesaurus.