Emtree

"Comprehensive and polyhierarchically structured, Emtree provides a consistent description of all biomedical terminology, allowing unrivaled drug and disease indexing. Over 56,000 preferred terms (of which more than 27,000 are drugs and chemicals) - more than twice as large as MeSH; More than 230,000 synonyms (with over 144,000 drugs and chemical synonyms); 7,500 explosion terms (terms that define the hierarchical structure); 78 subheadings (64 drug subheadings and 14 disease subheadings); 20,300 links to CAS registry numbers; All MeSH terms; Easy to search: each term has on average more than four synonyms, enabling easy mapping of your search terms; Comprehensive drug searching: Emtree includes chemical names, trade names, and laboratory/research codes as well as generic names; Up-to-date: the latest drugs, diseases, organisms and procedures are indexed as candidate terms throughout the year, and the most frequently used terms are added annually to Emtree. This means you can search using even the newest terms; Explosion (tree) searching: facilitated by Emtree's extensive hierarchical structure, with up to 12 levels, you can broaden and narrow your search; Polyhierarchical structure: no need to know 'where' terms are located in the Emtree structure, the Emtree tool will guide you; Natural language terminology: no need to know 'how' terms are defined in Emtree, just use natural language; Inclusive terminology: includes all MeSH terms and many Enzyme Commission (EC) numbers, so you can search using these terms as well."