Some databases have the option to search using subject headings, also referred to as subject terms, controlled vocabulary, and indexed terms. Subject headings are a set of pre-determined terms (a controlled vocabulary) describing concepts within a specific database. In most cases, subject headings are applied to database records by human indexers who have read the full-text to understand the main subjects discussed, although some databases use automation as well.
The following page works through subject heading search options available on the Ovid platform that is used for a number of databases such as MEDLINE, Embase, EBM Reviews (i.e. Cochrane Library), PsycINFO, etc. The examples and screenshots provided are from Ovid MEDLINE and may function or appear slightly different on other Ovid databases. Similar principles apply to other search platforms.
(Note: searching without subject headings is referred to as keyword searching. By default, many databases search for your keyword search terms in the bibliographic details of the record i.e. the article title, abstract, author keywords, as well as in the database-specific subject headings)
For example: the terms physical activity and exercise can be used to describe the same concept. The database will have a pre-determined term (subject heading) to search for records that are about the concept of physical activity or exercise, regardless of what words are used to describe the concept in the bibliographic details. For the same reason, we don’t have to worry about different spellings (ex. paediatrics vs pediatrics) for the same concept when searching with subject headings
For example: searching the subject heading that the MEDLINE database uses for the concept of exercise, presents a list of more specific types of exercise that you can easily choose to include or leave out (see further down the page)