Dictionary.net

A research and development program initiated by the National Library of Medicine to build an intelligent automated system that can understand biomedical concepts, words, and expressions and their interrelationships, and use this understanding to help users retrieve and organize information from a variety of machine-readable sources. The goal of the UMLS is to compensate for differences in the terminology of the disparate systems and for variations in user modes of expression. The UMLS project has produced four knowledge sources meant to be used by user interface programs. These are the Metathesaurus, the Semantic Network, the Information Sources Map, and the Specialist Lexicon.