Controlled vocabulary is the words and phrases used by a subject specialist when creating subject headings for an article, document, or book for a specific index or catalog. For example, the books in Carleton's library collection are assigned subject headings from the Library of Congress Subject Headings. Articles listed in JSTOR, PsycInfo, and other databases, are given subject headings by subject specialists, or indexers. These subject headings are then listed in a thesaurus designed for that database. This is meant to provide consistency and order in the chosen words and phrases.