Office of the Federal Register (OFR)

Thesaurus of Indexing Terms

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.

PDF (178 pages, 1034 KB)


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.

 Thesaurus Structure

Official indexing terms (included in the CFR Subject Index) appear in boldface black type, with all related terms under the subheading  See also". Variations on official terms (not included in the Subject Index) appear in red italicized text preceded by an asterisk, with the official terms under the subheading "See".

The Thesaurus is structured as an alphabetic list of all indexing terms with additional cross-references leading the user to preferred or related terms. Where appropriate, it also contains suggested cross-references to specific foods, chemicals, commodities and geopolitical entities.

Using the Thesaurus

The Office of the Federal Register uses the Thesaurus as the basis for the subject entries in the CFR Index, revised and published annually as of January 1. 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. However, these terms will not appear in the CFR Index.

Current Version

The Thesaurus is current as of April 1, 2024.

Contact Us

For questions about or to comment on the Thesaurus of Indexing Terms or the CFR Index email