Vocabulary Control and it's tools

The term “vocabulary control” refers to a limited set of terms that must be used to index documents, and to search for these documents, in a particular system. It may be defined as a list of terms showing their relationships and indicating ways in which they may usefully be combined to provide specific subject of a document. A certain degree of structure is introduced in a controlled vocabulary so that terms whose meanings are related are brought together or linked in some way. The opposite, an uncontrolled vocabulary (i.e. free vocabulary), is an unlimited set of terms drawn from natural language.