Find terms, their definitions, and related terms, using NLM's MeSH and UMLS Metathesaurus.

• Medical Subject Headings (MeSH) is NLM's controlled vocabulary thesaurus. MeSH terminology provides a consistent way to retrieve information that may use different terminology for the same concepts.

• NLM's Unified Medical Language System (UMLS) Metathesaurus contains information about biomedical concepts and terms from many sources.