Online Reference Sources

These are resources that professional indexers may find useful in their daily work. Please visit the Internet Public Library for more general reference sources.

Thesauri will be found by subject on this page. For additional resources, consult ASI’s list of online thesauri.

And, as always, ASI does not endorse or promote products, companies, political parties, religious groups, advertising or information found in web sites we provide links for.

General Reference Sources Specific Reference Sources


General Reference Sources


  • Dictionaries, Thesauri, and Other Language Tools
    • Acronym directory. Search only.
    • A compilation of dictionaries, glossaries and other language-related and writing tools. Also translation, etymology and puzzle-solving assistance.
    • The Free Dictionary. English, Medical, Legal, Financial, and Computer Dictionaries. With search engine.
    • The Free Thesaurus. Thesaurus of synonyms, antonyms, and related words from three sources: Collins Thesaurus of the English Language, The American Heritage Roget’s Thesaurus, and WordNet. Filter by part of speech to show only the results you want to see.
    • Geographic Name Thesaurus
    • iLoveLanguages. Information about and dictionaries for many languages, arranged alphabetically by language.
    • German/English Translation Service. This isn’t a Web page; the LEO translation services is a translation-by-email service. Put words you want to have translated into the email message body and receive a translation in reply. (Note that the service translated individual words, not sentences.) Send your email message to with no subject and the message body of your words-to-be-translated.
    • Language Dictionaries. List of language dictionaries.
    • Library of Congress Thesauri. Includes link to the Legislative Indexing Vocabulary (LIV).
    • Library of Congress Thesaurus for Graphic Material I and II. (NOTE there are two distinct and separate links: one for volume I and one for volume II.) If you are looking for a thesaurus of terms related to graphic materials, this is where you want to be exploring. For browsing and searching.
    • LookWayUp Dictionary. This dictionary and thesaurus site allows approximate spellings on look-up and combines a multilingual dictionary, thesaurus, translation, and other handy tools. The built-in thesaurus gives synonyms, antonyms, and up to 25 types of related terms.
    • Merriam-Webster Dictionary. Search only.
    • National Information Standards Organization (NISO) standards page includes access ANSI/NISO Z39.19 – 2005 Guidelines for the Construction, Format, and Management of Monolingual Controlled Vocabularies (Related international standard: ISO 2788). This standard presents guidelines and conventions for the contents, display, construction, testing, maintenance, and management of monolingual controlled vocabularies. It focuses on controlled vocabularies that are used for the representation of content objects in knowledge organization systems including lists, synonym rings, taxonomies, and thesauri. Available for a fee.
    • Netdictionary. This is an alphabetical reference guide to technical, cultural, and humorous terms related to the Internet. Browsing and searching.
    • Onelook dictionary. Search only. (For browsing, see You can choose to look up your word in one dictionary or through all of the variety of specialized and general dictionaries available. A great source! Contains listings for over 200 searchable dictionaries.
    • Online Dictionary of Language Terminology. The ODLT is an online dictionary of language terminology that consists of concise, simply worded explanations of terms that English speakers use to talk about the English language.
    • Online English Grammar.
    • The Wordsmyth English Dictionary-Thesaurus. Search only. Search for words, close matches, synonyms, and so on. Much more than a dictionary.
    • The World Bank Thesaurus. Search or browse by letter.
    • Transportation Research Thesaurus. The Transportation Research Thesaurus was developed to provide a tool to improve the indexing and retrieval of transportation information. The thesaurus covers all modes and aspects of transportation. A primary use will be to provide a common and consistent language between producers and users of the Transportation Research Information Services (TRIS) Database. The thesaurus is currently also used as an indexing tool for federal, state and university collections. The TRT Web site allows users to access terminology through Alphabetical, Hierarchical, Keyword In Context or Keyword Out of Context displays. The full display shows relationship of terms including SN (Scope Notes), UF (used for terms), BT (Broader Term), NT (Narrower Term), and RT (Related Term).
    • Dictionaries of computer terms.
    • Science glossaries.
    • Still can’t find it? Try this:
  • Encyclopedias, Collections of Information, and Fact Books
    • CIA World Factbook.
    • Encyclopædia Britannica. A classic and now completely free online.
    • Articles from Concise Columbia Electronic Encylopedia, Third Edition.
    • ERIC Thesaurus. ERIC (Educational Resources Information Center) is a national education database of bibliographic citations and digests, sponsored by the U.S. Department of Education. This online version of the ERIC Thesaurus provides immediate search access to portions of the ERIC database. The 40-member ERIC Vocabulary Review Group (VRG) presently oversees the Thesaurus development effort. Search only.
    • Flags of the World. An extensive site devoted to vexillology.
    • Geographic Names Information System. A service of the United States Geological Survey.
    • Still can’t find it? Try one of the following:

      • Encyberpedia (list of online encyclopedias).
      • Credo Reference (Formerly xrefer with access to over 50 dictionaries, fact books, and desktop encyclopedias not otherwise available online). SUBSCRIPTION basis only now but many libraries subscibe and you might be able to access it via your library membership!
  • Phone Directories, Organizational Listings, and Geographical Maps
  • Of Particular Interest to Indexers

Art and Architecture Reference Sources


  • The Art & Architecture Thesaurus. The AAT is a controlled vocabulary for describing and retrieving information on fine art, architecture, decorative art, and material culture. This database is created and maintained by the Getty Information Institute, and endorsed by library, archives, and museum professional groups.
  • The Union List of Artist Names. The ULAN is a database of biographical and bibliographical information on artists and architects, including a wealth of variant names, pseudonyms, and language variants. This database is created and maintained by the Getty Information Institute, and endorsed by library, archives, and museum professional groups.


Biographical Reference Sources


  • The Biographical Dictionary. This commercial site is now a Wiki so reliability could be questionable for some entries.
  • Biographical Directory of the United States Congress. Searchable biographical data on members of the U.S. Congress from 1774 to the present.
  • Political Graveyard. This database of historic cemeteries and political families offers brief biographical data on 53,115 (as of December, 1999) deceased politicians, diplomats, and judges, and is indexed in a number of ways, including an alphabetical index (by last name). The site also features a list of links, and some of those sites might also be helpful.


Business Reference Sources

[General Business Information] [Small Businesses, Self-Employment, and Working from Home] [Health in the Workplace] [ Finding Work] [Additional Business Reference Sites]


Computer and Technology Reference Sources



Health and Medicine Reference Sources


  • American Medical Writers Association (AMWA). The American Medical Writers Association was founded in 1940 to help medical authors improve their writing skills. Now, as then, AMWA strives to help biomedical communicators construct more effective communications by offering continuing education seminars, courses offered at our Annual Conference, and through our many publications.
  • Kinsey Institute The Kinsey Institute has at its site a thesaurus that deals with all aspects of sexuality. Although there is no direct link to their thesaurus, you can contact the librarian of the site for more information.
  • Martindale’s Health Science Guide. Thousands of health-related resources.
  • Medical Subject Headings (MeSH): on the WEB. These subject hierarchies are brought to you by the National Library of Medicine. MeSH is the most used thesaurus in publications for medical and health professionals.
  • Medicine Net. Lists of diseases and medications, in nonmedical language.
  • MEDLINE Plus. This is NLM’s consumer health site, with links to MEDLINE and a host of other medical info sources, including databases, web links, dictionaries, physician listings, organizations, etc.
  • Merck Manual. The most widely used medical text worldwide. Searchable.
  • National Rehabilitation Information Center (U.S) produced a thesaurus of rehabilitation terms.
  • PubMed, a service of the National Library of Medicine, provides access to over 11 million citations from MEDLINE and additional life science journals. PubMed includes links to many sites providing full text articles and other related resources. A tutorial is provided on the site as an aid to first-time searchers.
  • Reference.MD, Medical information from National Library of Medicine 2007 Medical Subject Headings, National Institutes of Health Unified Medical Language System, Drugs@FDA, Federal Drug Administration Adverse Event Reporting System. Medical concepts or drugs are presented as concept trees that you can drill into to see related concepts.
  • Ultimate Guide to Self-Employed Health Insurance, from
  • Sites dealing with health in the workplace

Legal Reference Sources



Science Reference Sources


  • Biological Sciences
    • Cell biology glossary. Browse only; requires browser’s “search” function. Hosted by the University of California Museum of Paleontology.
    • Phylogenetic glossary. Browse only; requires browser’s “search” function. Hosted by the University of California Museum of Paleontology.
  • Botany and Zoology Sciences
    • Botanical glossary. Browse only; requires browser’s “search” function. Hosted by the University of California Museum of Paleontology.
    • PLANTS National Database. Maintained by the USDA’s National Plant Data Center, this huge database can be searched by common or scientific name; reports accessible from the home page include invasive and noxious plants, threatened and endangered plants, wetland plants, and much more.
    • Zoology glossary. Browse only; requires browser’s “search” function. Hosted by the University of California Museum of Paleontology.
  • Chemistry and Biochemistry Sciences
    • Biochemistry glossary. Browse only; requires browser’s “search” function. Hosted by the University of California Museum of Paleontology.
    • CAS General Subject Vocabulary Helper Chemical Abstracts Service scientific and medical terms. CAS is the definitive source for chemical terms.
    • Periodic table of the elements.
    • Pesticide Common Names. Lists of common names (e.g., DDT, malathion, paraquat), molecular formulae (e.g., C13H17F3N4O4), Chemical Abstracts Registry Numbers (e.g. 50-00-0, 209866-92-2), systematic names (e.g., 2-tert-butyl-4,6-dinitrophenol); also hierarchical lists of pesticides.
  • Environmental and Earth Sciences
    • Ecological glossary. Browse only; requires browser’s “search” function. Hosted by the University of California Museum of Paleontology.
    • Geologic glossary. Browse only; requires browser’s “search” function. Hosted by the University of California Museum of Paleontology.
    • Solar-terrestrial physics glossary. Browse only; requires browser’s “search” function.
  • Physics, Astronomy, and Aerospace
    • Astronomy thesaurus. This thesaurus, compiled by Robyn M. Shobbrook and Robert R. Shobbrook provides access to the thesaurus in English, French, German, Italian, and Spanish. For browsing and searching.
    • PACS (Physics and Astronomy Classification Scheme). PACS is arranged hierarchically by subdivision (down to four levels) of the whole spectrum of subject matter in physics- and astronomy-related sciences. No longer being updated, but the 2010 edition linked here should be adequate for non-scientist users.
    • Physics laws list. This glossary contains laws, principles, effects, paradoxes, limits, constants, experiments, and thought experiments in physics–an absolute must for physics junkies and indexers. Browse only.
    • Thermonuclear fusion glossary.
    • Solar-terrestial physics glossary. Browse only; requires browser’s “search” function.
    • Space flight glossary. Search and browse.
  • Science, Technology, and Industry


Technical Writers’ Resources


  • The Journal of Electronic Publishing. Published by the University of Michigan Press.
  • TECHWR-L. Anything related to any facet of technical communication (practice, research, teaching) is appropriate for this discussion list.


Libraries and Library Sciences




Miscellaneous References