Library of Congress Subject Headings

Library of Congress Subject Headings

The "Library of Congress Subject Headings" (LCSH) comprise a thesaurus (in the information technology sense) of subject headings, maintained by the United States Library of Congress, for use in bibliographic records. LC Subject Headings are an integral part of bibliographic control, which is the function by which libraries collect, organize and disseminate documents. LCSHs are applied to every item within a library’s collection, and facilitate a user’s access to items in the catalogue that pertain to similar subject matter. If users could only locate items by ‘title’ or other descriptive fields, such as ‘author’ or ‘publisher’, they would have to expend an enormous amount of time searching for items of related subject matter, and undoubtedly miss locating many items because of the ineffective and inefficient search capability.

An art and science

Subject heading classification is a human and intellectual endeavor, where trained professionals apply topic descriptions to items in their collections. Naturally, every library may choose to categorize the subject matter of their items differently, without a uniform agreed upon standard. The widespread use and acceptance of the "Library of Congress Subject Headings" facilitates the uniform access and retrieval of items in any library in the world using the same search strategy and LCSH thesaurus, if the correct headings have been applied to the item by the library. Thusly, LCSH decisions involve a great amount of debate and even controversy in the library community.

Despite LCSH's wide-ranging and comprehensive scope, there are libraries where the use of LCSH is not ideal or effective. To deal with these types of collections and user communities, other subject headings may be required. The United States National Library of Medicine developed Medical Subject Headings (MeSH) to use on its many health science databases and collection. Many university libraries may apply both LCSH and MeSH headings to items. In Canada, the National Library of Canada worked with LCSH representatives to create a complementary set of Canadian Subject Headings (CSH) to access and express the topic content of documents on Canada and Canadian topics.

LCSH policy issues

Historically, issues have revolved around the terms employed to describe racial or ethnic groups. Notable has been the terms used to describe African-Americans. Until the 1990s, the LCSH administrators had a strict policy of not changing terms for a subject category. This was enforced to tighten and eliminate the duplication or confusion that might arise if subject headings were changed. Therefore, one term to describe African-American topics in LCSH was ‘Afro-American’ long after that term lost currency and acceptance in the population. LCSH decided to allow some alteration of terms in 1996 to better reflect the needs and access of library users. Nevertheless, many common terms, or ‘natural language’ terms are not used in LCSH, and may in effect limit the ability for users to locate items. There is a growing tradition of research in Library and Information Science faculties about the cultural and gender biases that affect the terms used in LCSH, which in turn may limit or deprive library users access to information stored and disseminated in collections. A notable American Library Science scholar on this subject is Sanford Berman.

Using LCSH

The Subject Headings are published in large red volumes (currently five), which are typically displayed in the reference sections of research libraries. They may also be searched online in the [ Library of Congress Classification Web] , a subscription service, or free of charge at [ Library of Congress Authorities] . The Library of Congress issues weekly updates. Once a library user has found the right subject heading they are an excellent resource for finding relevant material in your library catalogue. Increasingly the use of hyperlinked, web-based Online Public Access Catalogues, or OPACs, allow users to hyperlink to a list of similar items displayed by LCSH once one item of interest is located. However, because LCSH are not necessarily expressed in natural language, many users may choose to search OPACs by keywords. Moreover, users unfamiliar with OPAC searching and LCSH, may incorrectly assume their library has no items on their desired topic, if they chose to search by ‘subject’ field, and the terms they entered do not strictly conform to a LCSH. For example ‘body temperature regulation’ is used in place of ‘thermoregulation’. Thus the easiest way to find and use LCSH is to start with a ‘keyword’ search and then look at the Subject Headings of a relevant item to locate other related material.


Despite their limitations, LCSH are widely used in library catalogs in North America and around the world. They should not be confused with the Library of Congress Classification, which does not attempt to evaluate the subject content of items, but rather broadly categorizes the item in a subject hierarchy. Many libraries, especially public and school libraries will use the Dewey Decimal Classification system for organizing collections, but will employ LCSH for accessing material by topic.

ee also

* Library of Congress Classification

External links

* [ Library of Congress Cataloging home page]
* [ Cataloging Distribution Service] - primary source of Library of Congress Subject Headings
* [ Library of Congress Authorities] - allows users to look through the subject headings at no charge
* [] - is a Linked Data, SKOS representation of the subject headings for the semantic web; periodically updated

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