Library of Congress Subject Headings

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The Library of Congress Subject Headings ( LCSH ) form a thesaurus (in the sense of library science ) with subject headings that is maintained by the Library of Congress in Washington. The LC Subject Headings help libraries collect, organize and distribute documents. LCSHs are assigned to each medium in the library inventory and make it easier for users to find other relevant literature on their subject. If users were only able to search for media using the “title” or other formal, non-content-related fields such as “author” or “editor”, they would have to spend a lot of time finding media on related topics. Undoubtedly they would miss out on many relevant titles due to the ineffective search strategy for the objective search. Systems in other languages ​​that are comparable to the LCSH are the German subject headings authority file (SWD) and the French Répertoire d'autorité-matière encyclopédique et alphabétique unifié (RAMEAU).

An art and a science

Keywords are a task that requires a high level of knowledge and experience. Trained specialists assign the appropriate topic to the individual media in their holdings in the form of controlled vocabulary. Each library is free to use keywords for its holdings as it sees fit, without using a generally established standard. However, the use and broad acceptance of the Library of Congress Subject Headings facilitates standardized access and finding of media in all libraries in the world that also use the LCSH thesaurus, provided that the correct keywords have been assigned by the library. Against this background, it is understandable that decisions about subject headings often lead to controversial discussions in the professional world.

Despite the wide range of subjects covered by the LCSH Thesaurus, some libraries may find that its use is not ideal or effective. In order to do justice to such stocks and their users as best as possible, there is a need for other keyword systems. The United States National Library of Medicine (NLM) developed the Medical Subject Headings (MeSH). These are used for their numerous medical databases and holdings. Many American university libraries use both the LCSH and the MeSH.


The LCSH are published in book form in five large red volumes. These are often kept in the holdings of scientific libraries (especially in the USA). The subject headings are made available on the Internet in the Library of Congress Classification Web, which is subject to a fee. The Library of Congress publishes an updated version weekly. As soon as a library user has found the appropriate subject headings, he has an excellent tool for finding literature relevant to his topic in his library's catalog (if the LC Subject Headings are used there). The use of online catalogs (OPACs) accessible via the Internet is increasingly making it possible for users, as soon as they have found a title relevant to their topic in the catalog, to access a large number of related literature by linking the keywords assigned there with the general catalog that was tagged with the same LC Subject Heading. The online catalog of the Library of Congress also offers the possibility of a factual search with the help of the LCSH. However, since the LCSH do not necessarily have to correspond to natural language, many users prefer to use keywords for their search in the online catalog.

In addition, library users who are not familiar with searching in the OPAC or LCSH could falsely assume that their library does not have any literature on the topic they require if they use the keyword search and do not standardize the terms they use The keyword and there is no reference to the correct expression. For example, the Library of Congress uses the keyword “body temperature regulation” instead of the term “thermoregulation”. Therefore, the easiest way to find a keyword and to use the LCSH is to first carry out a plausible keyword search, then select the appropriate keywords from the hits and use them to initiate a keyword search in order to find as much literature as possible on the desired topic.


Despite their weak points, the LCSH are used in many North American library catalogs and also worldwide. They must not be confused with the Library of Congress Classification , which does not attempt to present the thematic content of media directly, but rather classifies the title within a thematic hierarchy that branches off from general to specific. Many libraries, especially public libraries and school libraries, use the Dewey Decimal Classification to list their holdings, but use the LCSH to catalog them.

See also

Web links

Individual evidence