An ontology is not a terminology, and a terminology is not an ontology: they have not the same goal. Nevertheless, ontology is today one of the most promising perspectives to Terminology (e.g. for IT applications).
An ontoterminology is a terminology whose conceptual system is a formal ontology. This new paradigm was introduced in 2007. Based on the fact that linguistic and conceptual dimensions do not match, ontoterminology makes explicit the double dimension of Terminology. Ontoterminology preserves the linguistic diversity taking into account multilingualism and allows to standardize domain knowledge.
For more information see: http://www.ontoterminology.com