For questions related to dictionary-like structures in programming, mainly to Semantic Web vocabularies. Please do not use in place of the "terminology" tag.
In Semantic Web
In the Semantic Web field, a controlled vocabulary is a set of URIs used to identify things, relations or classes.
A vocabulary with well-developed subsumption (subclass-superclass) relations is often called a taxonomy.
A taxonomy with well-developed non-subsumption relations is often called an ontology.
See also: