The Thesaurus of Indexing Terms is a basic indexing vocabulary for Federal regulations that are published in the Federal Register and the Code of Federal Regulations.

Scope
Any document published in the Rules and Regulations or the Proposed Rules sections of the daily Federal Register must include a list of subjects for each CFR part affected by the regulatory text. Agencies must use the terms provided in the Thesaurus of Indexing Terms (1 CFR 18.20). These indexing terms are broad enough for use by all agencies while still helping users find specific information.

Using the Thesaurus
The Office of the Federal Register uses the Thesaurus as the basis for the subject entries in the Subject Index. Federal agencies use the Thesaurus to prepare the "List of Subjects" which appears in rule and proposed rule documents published in the Federal Register.

Agencies must use at least one official thesaurus term. They are also encouraged to use terms of greater specificity such as "apples" or "apricots" instead of "commodities", and specific chemicals, minerals or foreign nations where regulations are narrowly focused. Agencies may then include other relevant terms in the List of Subjects that are not from the Thesaurus.