Subject headings, descriptors and thesauri are "controlled vocabulary." They are lists of pre-defined, carefully selected words and phrases used to identify and classify information. Most databases include a Thesaurus or Subject Terms that list subjects, alternative terms and details for topics. Use the Thesaurus to narrow your results or combine its use with keyword searching for more focused results.
Identify all the major concepts of your thesis or research topic. Then use the thesaurus or subject index to locate, explore and select descriptors for each concept of your topic. for example, in opens new windowCommunication Source:
Whereas the common keyword search is based on an exact word match, a subject or thesaurus search locates records by assigned subject or descriptors.
searching with controlled vocabulary in a subject index or thesaurus allows you to more precisely retrieve relevant information on your topic, illustrates relationship between related terms and helps you identify synonyms and broader and narrower terms.
Keyword and subject terms searching can be combined. For example, rather than guessing what keywords to use consider doing a thesaurus (controlled vocabulary) search first. Review and assess your results. Then, add a keyword search to the query or use Search History to combine searches.