Medical Subject Heading. A controlled vocabulary term used by all the indexers in an organization to ensure consistency in assigning terms to articles (or records) on the same topic. They are also used in searching to avoid having to think of all the possible words that various authors could have used to express the same concept. For example, the MeSH heading AGED is assigned instead of aging, older, elderly, senior citizen, geriatric person, etc. that might appear in the title or abstract of the article.
The National Library of Medicine's controlled vocabulary thesaurus is called Medical Subject Headings. MeSH consists of a set of terms or subject headings that are arranged in both an alphabetic and a hierarchical structure to show the relationship between related terms and to permit searching at various levels of specificity, from narrower to broader.