Fig. 1

Part of the entries for the term acute tubulointerstitial nephritis and the direct ascendant term tubulointerstitial nephritis. The HPO terms have a unique identifier, a name, and many of them have textual descriptions and synonyms, that is, words that have the same meaning, or more or less the same meaning as another word, according to Wikipedia. In the format provided by the Open Biomedical Ontology (OBO) Foundry, the type of a synonym may fall into one of the following categories: exact, broad, narrow, and related. The hierarchical relationships between two terms are expressed using the is-a entry