Subject headings, descriptors and thesauri terms, also called "controlled vocabulary," are lists of pre-defined, carefully selected words and phrases used to identify and classify information.

Most databases include a Thesaurus or Subject Terms link in the menu bar.

Once you find a relevant term, in addition to alternative terms, narrower terms and/or broader terms. are also listed Use the Thesaurus to narrow your results or combine its use with keyword searching for more focused results.

Identify each concept of your topic. For example, in opens new windowCommunication Source:

1. Click Thesaurus in the top menu bar.
2. Type your term in the Browsing Thesaurus text box and select a browse function, (Term Begins With, Term Contains, or Relevancy Ranked) Click Browse.
3. To display details of a term, click the term.
4. Click the checkbox in front of the term(s) to include it in the search, then click Add to move the thesaurus terms into the search text box.
5. Click Search to run the search or click browse to find another descriptor.
   
   

Whereas the common keyword search is based on an exact word match, a subject or thesaurus search locates records by assigned subject or descriptors.

Using controlled vocabulary in a subject index or thesaurus:

• allows you to more precisely retrieve relevant information on your topic,
• illustrates relationship between related terms, and
• helps you identify synonyms and broader and narrower terms.

Combine keyword and subject term searching.
For example, rather than guessing what keywords to use consider doing a thesaurus (controlled vocabulary) search first. Review and assess your results. Then, add a keyword search to the query or use Search History to combine searches.