The Medical Subject Headings (MeSH®) are developed and maintained by the U.S. National Library of Medicine (NLM).
The MeSH thesaurus is a controlled vocabulary used for indexing, cataloging, and searching for biomedical and health-related information and documents. It enables retrieval systems, such as PubMed, to provide subject searching of data.
MeSH consists of sets of terms naming descriptors in a hierarchical structure that permits searching at various levels of specificity.
The three basic types of MeSH records are Descriptors, Qualifiers (subheadings), and Supplementary Concept Records.
MeSH has over 28,000 Descriptors; 82 topical Qualifiers; more than 240,000 Supplementary Concept Records; and over 90,000 entry terms.
MeSH is continually updated by NLM health science subject specialists. New terms from scientific literature and research can be recommended for addition to MeSH.
MeSH is also included in RxNorm.
The Metathesaurus also includes the following MeSH translations:
The MeSH vocabulary is designed for use by NLM for indexing and searching the MEDLINE database of journal citations and cataloging the NLM collection.
MeSH is used by indexers, subject catalogers, online searchers, and in retrieval systems.
A revised MeSH vocabulary is released annually; Descriptors and Qualifiers are updated annually while Supplementary Concept Records are updated continuously.
Metathesaurus Update Frequency
MeSH is an updated source in each Metathesaurus release. Descriptor and Qualifier changes appear in the November release while Supplementary Concept Record changes appear in each release.