Tax treaty definitions clarify residence, enterprise scope, competent authority, fiscal year and interpretation rules under domestic tax law. The Convention supplies core definitions governing its application between Hungary and India: territorial scope; who counts as a Contracting State, person, company, enterprise and national; the concept of international traffic; each State's competent authority; fiscal year definitions; and a limiting definition of tax excluding penalties. It mandates that undefined terms be interpreted according to the applying State's domestic tax law at the relevant time, with tax-law meanings prevailing over other domestic-law meanings.