If everybody agrees to say that ontology is at the core of the digital society, it remains to agree on what ontology is. For example, the ISO standards offer more than forty definitions of ontology ranging from a conceptual system to a structured vocabulary. However, while we can agree on a definition of ontology, ontologies in the same domain may differ and need to be harmonized. There are different approaches, methods and techniques for ontology terminology harmonization (including ontology terminology alignment) ranging from a linguistic one focusing on terms to a conceptual one focusing on concepts and their relationships. These issues will be studied from the point of view of ISO on Terminology where a term is a verbal designation of a concept, and a concept is a unique combination of characteristics This talk will be illustrated with the ISO 860 Standard on “Harmonization of concepts and terms”.