Unified Medical Language System

In 1989 by the U.S. National Library of Medicine initiated Unified Medical Language System ( UMLS ) is a project that terminologies biomedical resources such as online databases and medical dictionaries will align with each other. This is done by concepts and relations of various existing databases are related to one another, that is, ontologies are made. The system is continually evolving, the use is free after registration. The UMLS currently includes over 100 conceptual systems biomedicine.

It covers one million biomedical concepts with about five million concept names. Examples of the 100 controlled vocabularies and classifications are ICD -10, SNOMED, LOINC or MeSH. The system includes three areas lexicon Metathesaurus, Semantic Network, and SPECIALIST.