Keywords are words used to index or tag documents, which are typically uncontrolled terms. (In other words are keywords one kind of metadata, which are typically different from, for example,  descriptors and subject headings).



A keyword(s) is a word or group of words, possibly in lexicographically standardized form, taken out of a title or of the text of a document characterizing its content and enabling its retrieval (ISO norm 5963; 1985)



Wellisch (1995, p. 248-253) is an entry about keywords. He writes (p. 248):

"The term "keyword" is used in indexing in two quite different senses:  (1) the first word of a heading; and (2) a significant word taken from the text of a document and used in a heading (but not necessarily as the first word in it). Since these two senses of the term are quite different, it is important to distinguish clearly between them. Keywords in the first sense are now generally called LEAD TERMS, while the second sense is currently the best known one for "keyword"".


Wellisch (1995, p. 480) writes: "Keyword or term lists are essentially stripped-down versions of subject heading lists with little or no synonym control and often lacking cross-references; they generally do more harm than good for indexing purposes".



Identifier is a special kind of uncontrolled keywords to be used together with descriptors. KeyWord Plus is a kind of keywords in the citation databases from ISI. They are made by an algorithm based on words in titles of cited papers. Author supplied keywords are indexing terms suggested by the author of a given paper.



The functionality of uncontrolled versus controlled vocabulary has been much discussed in Library and Information Science (LIS).





Ansari, M. (2001). Descriptors and title keywords: Matching in medical PhD dissertations. Quarterly Journal of the National Library of the Islamic Republic of Iran, 12(2), 23-33.

Boger, Z., Kuflik, T., Shoval, P., & Shapira, B. (2001). Automatic keyword identification by artificial neural networks compared to manual identification by users of filtering systems. Information Processing and Management , 37(2), 187-198.

Craven, T. (2004). Variations in use of meta tag keywords by web pages in different languages. Journal of Information Science , 30(3), 268-279.

Craven, T. (2005). Web authoring tools and meta tagging of page descriptions and keywords. Online Information Review , 29(2), 129-138.

Gbur, E.E., & Trumbo, B.E. (1995). Key words and phrases - The key to scholarly visibility and efficiency in an information explosion. The American Statistician , 49, 29-33.

Gil-Leiva, I. & Alonso-Arroyo, A. (2007). Keywords given by authors of scientific articles in database descriptors. Journal of the American Society for Information Science and Technology, Published Online: 25 Apr 2007

Gross, T., & Taylor, A.G. (2005). What have we got to lose? The effect of controlled vocabulary on keyword searching results. College & Research Libraries , 66(3), 212-230.

Hartley, J., & Kostoff, R.N. (2003). How useful are key words in scientific journals? Journal of Information Science , 29(5), 433-438.

International Association for Standardization (ISO). (1985). Documentation. Methods for examining documents, determining their subjects, and selecting indexing terms (ISO 5963:1985). Geneva, Switzerland: International Association for Standardization.

Jones, S., & Paynter, G.W. (2002). Automatic extraction of document keyphrases for use in digital libraries: Evaluation and applications. Journal of the American Society for Information Science and Technology , 53(8), 653-677.

Taghva, K., Borsack, J., Nartker, T., & Condit, A. (2004). The role of manually-assigned keywords in query expansion. Information Processing & Management , 40, 441-458.

Tillotson, J. (1995). Is keyword searching the answer? College and Research Libraries , 56(3), 199-206.

Turney, P.D. (2000). Learning algorithms for keyphrase extraction. Information Retrieval , 2(4), 303-336.

Voorbij, H.J. (1998). Title keywords and subject descriptors: A comparison of subject search entries of books in the humanities and social sciences. Journal of Documentation , 54(4), 466-476.

Wellisch, H. H. (1995). Indexing from A to Z. 2nd. ed. New York: H. W. Wilson.



See also: Controlled vocabulary; KWIC / KWAC / KWOC





Birger Hjørland

Last edited: 12-05-2007