The next stage in managing the controlled vocabulary is to introduce some internal structure into each facet. Among other things, it's necessary to identify synonyms and near synonyms in the vocabulary, and to establish relationships of hierarchy. It's therefore useful to take a more detailed look at the thesaural relationships and how they are used to express these in the alphabetical display.

The principal thesaural relationships

The form of cross-referencing in thesauri is now formalized in a standard manner, and the great majority of thesauri use five abbreviated codes to indicate the different kinds of relationship between an entry term and other terms in the vocabulary. These are:

Other codes

In addition, the code SN (scope note) is used when it is necessary to explain or define a term or otherwise indicate how and where it should be used. The word ‘scope’ is used in the sense of the range of meaning of the term, and any limitations on that meaning. Scope notes can take the form of definitions, explanations, or instructions on the application of a term. They may also include examples of how a term should be used.

There are other examples of codes besides those used to express interterm relationships. Both the new British Standard and the American Standard include HN (history note) for information about when terms were added or amended and other editorial details of that kind. Some thesauri employ a formal code for notations, such as CC (classification code). The British Standard also includes DEF (definition) for thesauri which explicitly distinguish these from other aspects of the scope note.

Top term

The relationship TT (or top term) may be encountered in a multidisciplinary thesaurus, indicating the general subject area in which a term occurs.