An ontology is an explicit specification of a conceptualization.
. “Toward principles for the design of ontologies used for knowledge sharing”. International Journal of Human-computer Studies, 43(5-6), pp. 907-928. [p.908/2. Ontologies as a specification mechanism/Pr2/S1]
ontology: (sense 1) a logical theory which gives an explicit, partial account of a conceptualization; (sense 2) synonym of conceptualization.
Guarino & Giaretta, Ontologies and knowledge bases: towards a terminological clarification. 1995. In N. MARS, Ed. Towards Very Large Knowledge Bases: Knowledge Building and Knowledge Sharing. pp.25–32. Amsterdam: IOS Press. [p.31/7 A Simple Glossary/Pr8/S1/S1]