Tax treaty definitions determine residency, national status and enterprise scope, with undefined terms governed by domestic tax law. The provision defines territorial scope, persons, companies, enterprises, international traffic, competent authority and national status for the India-Iran tax convention, and provides that any term not defined in the convention shall, unless context otherwise requires, have the meaning it has at the relevant time under the domestic tax law of the Contracting State applying the Agreement, with that tax-law meaning prevailing over other domestic-law meanings.