Free Blogger Templates

Controlled Vocabulary

Controlled Vocabulary

Controlled Vocabulary refers to an established list, organized arrangement, or database of preferred terms and phrases (usually subject or genre/form terms) in which all terms and phrases representing a concept are brought together. A controlled vocabulary is usually listed alphabetically in a subject headings list or thesaurus of indexing terms.

In a controlled vocabulary a preferred term or phrase is designated for use in surrogate records in a retrieval tool (e.g., bibliographic records in the library catalog), the non-preferred terms have references from them to the chosen term or phrase, and relationships among used terms are identified (e.g., broader terms, narrower terms, related terms). There may also be scope notes.

A cataloger or indexer must select terms from a controlled vocabulary when assigning subject headings or descriptors in a bibliographic record to indicate the subject of the work (e.g. a book) in a library catalog, bibliographic database, or an index.

Controlled vocabularies provide a way to organize knowledge for subsequent retrieval. They are used in subject indexing schemes, subject headings, thesauri, taxonomies, and other knowledge organization systems. Controlled vocabulary schemes mandate the use of predefined, authorized terms that have been preselected by the designers of the schemes, in contrast to natural language vocabularies, which have no such restriction.

Note: The process of creating, maintaining, and using a controlled vocabulary is called Vocabulary Control.

Janis L. Young and  Daniel N. Joudrey¹ describe Controlled Vocabulary as below:

What is a controlled vocabulary? 
  • A standardized subject language used to describe the contents of the resources.
  • They generally include:
    • One term chosen as the preferred term
    • Control of its synonyms
    • Disambiguation among homographs/homonyms 
    • Identification of relationships among the terms
    • Cross-references

For consistency and improved retrieval, libraries and other information institutions attempt to suppress the anarchy of natural language when it comes to describing the aboutness of resources. Subject cataloging is more consistent when the vocabulary that is used is controlled.

The main objective of vocabulary control is to promote the consistent representation and comprehensive searching of subject matter.

This is achieved through the control of synonymous and nearly synonymous terms, by distinguishing among homographs and homonyms, and by linking together terms whose meanings are related in some fashion (identifying broader, narrower, and related terms).

But the use of controlled subject languages is only part of subject cataloging; the other part involves classification.

Some examples of Controlled Vocabulary are: 

1. Subject Heading Lists (e.g. LCSH, SLSH)
2. Authority Files (e.g. LCNAF)
3. Taxonomies
4. Alphanumeric Classification Schemes (e.g., LCC, DDC, UDC)
5. Thesauri
6. Ontologies
7. Folksonomies

A classic and widely used form of Controlled Vocabulary is the Subject Heading List. It is described below:

Subject Heading List is the printed or published list of subject headings which may be produced from the subject authority file maintained by an organization or individual.

Subject heading list contains the preferred subject access terms (controlled vocabulary) that are assigned as an added entry in the bibliographic record which works as an access point and enables the work to be searched and retrieved by subject from the library catalog database. The controlled vocabulary identifies synonyms terms and selects one preferred term among them to be used as the subject heading. For homonyms, it explicitly identifies the multiple concepts expressed by that word or phrase. In short, vocabulary control helps in overcoming problems that occur due to natural language of the document’s subject. Hence, if vocabulary control is not exercised different indexers or the same indexer might use different terms for the same concept on different occasions for indexing the documents dealing with the same subject and also use a different set of terms for representing the same subject at the time of searching. This, in turn, would result in ‘mis-match’ and thus affect information retrieval. Cross-references are used with headings to direct the user from terms not used as headings to the term that is used, and from broader and related topics to the one chosen to represent a given subject.

Subject heading lists may have provision for the construction of pre-coordinated indexing strings including headings, plus rules for combining the single terms in strings and one or more levels of subheading. Based on these rules a subject heading may also be subdivided by the addition of form subdivisions, geographical subdivisions, chronological subdivisions, and topical subdivisions to add greater specificity.

Two popular subject heading lists are Library of Congress Subject Headings (LCSH) and Sears List of Subject Headings.

Examples based on Library of Congress Subject Headings (LCSH) following principles of assigning subject headings as described in Subject Headings Manual of Library of Congress:

English literature—20th century—History and criticism.
Construction industry—United States.
India—History—Autonomy and independence movements.
Piano music (Jazz)—France—History.
Aging—Egypt—Psychological aspects.

Following is an example of LCSH heading “Hotels” from Library of Congress Linked Data Service


Hotels, taverns, etc

Broader Terms
Hospitality industry

Narrower Terms
All-suite hotels
Allergen-free accommodations
Bed and breakfast accommodations
Gay accommodations
Haunted hotels
Historic hotels
Hotel chains
Hotel lobbies
Imaginary hotels
Nonsmoking accommodations
Park lodging facilities
Safari lodges
Single-room occupancy hotels
Tourist camps, hostels, etc

Related Terms
Taverns (Inns)

Earlier Established Forms
Hotels, taverns, etc

LC Classification

Subject headings, like access points based on author names and titles, serve the dual function of location and collocation. Subject heading lists are used by library catalogers to aid them in their choice of appropriate subject headings and to achieve uniformity. Subject Headings and thesauri are one of the two methods used to facilitate subject access to library materials. The other is library classification. Classification organizes knowledge and library materials into a systematic order according to their subject content, while subject headings provide access to documents through vocabulary terms. Subject Headings or Thesauri can assign multiple terms to the same document, but in classification, each document can only be placed in one class.

In a MARC bibliographic record Subject Heading is given in a 6XX field, consisting of either a single element in an $a subfield or of an $a subfield followed by subdivisions in $v, $x, $y, and/or $z subfields, that designates what a work is or what it is about. 



1. Janis L. Young and  Daniel N. Joudrey, Library of Congress, "Library of Congress Subject Headings: Online Training," (accessed March 17, 2020).


Article Title
  • Controlled Vocabulary

Website Name
  • Librarianship Studies & Information Technology


Last Updated
  • 2020-03-22

Original Published Date
  • 2020-03-22

  • Help us improve this article! Contact us with your feedback. You can use the comments section below, or reach us on social media.

Post a Comment