United States National Library of Medicine

NLM

The world's largest medical library, maintaining critical biomedical vocabularies and health metadata standards.

Government Agency Active

The United States National Library of Medicine (NLM), a component of the National Institutes of Health, is the world's largest medical library. Located in Bethesda, Maryland, NLM develops and maintains essential biomedical metadata standards and controlled vocabularies including MeSH (Medical Subject Headings), the UMLS (Unified Medical Language System), and the NLM Metadata Schema. It also operates PubMed and MEDLINE, which are foundational resources for health sciences information retrieval worldwide.

Standards (5)

Book Interchange Tag Suite

(BITS)

An XML tag suite extending JATS to encode the full text and metadata of scientific books.

Technical Specification active National Center for Biotechnology Information / National Library of Medicine Est. 2012

Journal Article Tag Suite

(JATS)

An XML tag set for marking up the full text and metadata of scholarly journal articles.

Technical Specification active National Information Standards Organization / National Library of Medicine Est. 2002

Medical Subject Headings

(MeSH)

A hierarchical thesaurus of 30,000 descriptors for indexing biomedical literature in PubMed.

Vocabulary / Thesaurus active U.S. National Library of Medicine Updated January 21, 2026

NCBI Taxonomy Database

The authoritative classification of over 2.5 million organisms across all NCBI sequence databases.

Vocabulary / Thesaurus active National Center for Biotechnology Information (NCBI) Est. 1991

NLM Classification

(NLMC)

Organizes biomedical library collections with alphanumeric schedules for preclinical and clinical sciences.

Encoding Scheme / Value Vocabulary active National Library of Medicine Est. 1951