Library of Congress Subject Headings

The Library of Congress Subject Headings (LCSH) comprise a thesaurus (in the information science sense, a controlled vocabulary) 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. It was first published in 1898, a year after the publication of Library of Congress Classification (1897). The last print edition was published in 2016. Access to the continuously revised vocabulary is now available via subscription and free services.

Subject headings are normally applied to every item within a library's collection and facilitate a user's access to items in the catalog that pertain to similar subject matter, in order to save time finding items of related subject matter. Only searching for items by 'title' or other descriptive fields, such as 'author' or 'publisher', would take more time and potentially miss locating many items because of the ineffective and inefficient search capability.