Subject headings, descriptors and thesauri terms are examples of "controlled vocabularies." They are lists of pre-defined, carefully selected words and phrases used to classify and organize information. Controlled vocabulary, which varies with discipline and database, describes the general content of an information unit, such as a book, an article, or an essay. Searching with a database subject index or thesaurus allows you to more precisely retrieve relevant information on your topic, view relationship between related terms, and identify synonyms and broader and narrower terms.

Change the search fields:
In the All fields drop-down menu, choose a relevant subject then enter your term and click the magnifying glass icon to search.

Use the ATLA Thesaurus:
Click Subjects and choose ATLA--Subject Thesaurus from the drop-down menu. The image below shows the subject thesaurus results for church history. Mark those subjects that match your search needs, click the Add to search button, and then search.

Change the search field by choosing a field listed in the All fields drop-down menu.

Use the Subjects option to identify narrower and broader subjects. Mark those subjects that are relevant to you search, click the Add to search button, and then search. Add additional terms as needed to refine your results.