Tax treaty definitions define territorial scope and core terms to govern tax allocation and administrative competence. Article 3 provides treaty definitions: it fixes the territorial scope of each Contracting State, defines tax for Convention purposes (excluding related amounts and penalties), and prescribes definitions for 'person', 'company', 'enterprise of a Contracting State', 'national', 'competent authority', 'international traffic' and 'fiscal year'. It requires that any term not defined in the Convention be given the meaning it has under the domestic law of the Contracting State applying the Convention, unless the context otherwise requires.