A thesaurus can be used for several different purposes. It is mainly used for information retrieval, in one way or another. We use it in information retrieval both on the search end and in the tagging of the records. We could use it in searching and not indexing or in indexing but not in searching; the possibilities are listed by Aitchison, Gilchrist, and Bawden in Thesaurus construction and use: a practical manual:

  • thesaurus used both in indexing and in searching [“The classic thesaurus”]
  • thesaurus used in indexing, but not in searching [“The indexing thesaurus”]
  • thesaurus used in searching, but not in indexing [“The search thesaurus”]
  • thesaurus used in neither case

People might intend to use their thesaurus for both indexing and searching, but unintentionally limit the actual usage to just indexing. Frequently, when people go to all the labor to tag their data, they put it into a search software application and the software doesn’t use it; a wasted effort. It is the search implementation that makes a difference as to how that indexing is used.

In addition to information retrieval, a thesaurus can also be used as a guide to the field — it might just be a browseable list, but it is a good way to learn about the field.

A thesaurus can be monolingual or multilingual. Multilingual thesauri are mostly concept-based; generally, a term record addresses the same concept in different languages. This can be useful for translation efforts, as well as multilingual indexing and search.

As knowledge organization systems, thesauri can be used to influence people’s thinking. After all, when you are presenting that outline of knowledge for your organization in a thesaurus, you are defining the relationships and categories of various concepts.

Marjorie M.K. Hlava
President, Access Innovations