Subject cataloging depends on lists of controlled subject access vocabulary and thesauri. This site provides access to free lists for:
LC Linked Data Services: Authorities and Vocabularies provides access to commonly found standards and vocabularies both in interactive search and machine access. It now includes BIBFRAME Works (works and expressions) and Instances (manifestations).
This searchable thesaurus is a list terms representing research topics in the field of education. They are assigned to every document in the ERIC digital library to describe its subject content. ERIC is a digital library of education research, sponsored by the U.S. Department of Education.
OCLC Bibliographic Formats and Standards MARC field 6xx describes categories of controlled and uncontrolled subject access terms for the MARC21 Communications Standard. See each field for coding of the Sources Codes for Vocabularies, Rules, and Schemes (Library of Congress maintained list).
Source Codes for Vocabularies, Codes, and Schemes is maintained by the Library of Congress Network Development and MARC Standards Office. These codes are used in MARC cataloging records and in other metadata description for collections. Global vocabularies are represented, including U.S. federal government vocabularies and thesauri. Some vocabularies are linked to sources.
The National Agricultural Library Thesaurus and Glossary are online vocabulary tools of agricultural terms in English and Spanish, cooperatively produced by the National Agricultural Library, USDA, and the Inter-American Institute for Cooperation on Agriculture, and others. The Thesaurus is used to select controlled vocabulary terms for subject indexing of AGRICOLA, PubAg and other databases. Search the Thesaurus in English or Spanish.
AGRICOLA is the U.S. Department of Agriculture National Agricultural Library (NAL) online catalog.
The Plain Language materials from the Centers for Disease Control and Prevention offers plain language equivalents to medical terms and phrases. These are useful for cataloging and metadata description, summaries, and even uncontrolled subject vocabularies.