Treaty definitions set scope of 'tax' and 'person', guiding interpretation and competent authority for treaty application. Article 3 defines key treaty terms: 'India' (territory including maritime zones), 'Czechoslovakia' (Czechoslovak Socialist Republic), 'tax' (Indian or Czechoslovak tax), 'person' and 'company' (as defined by each State's taxation laws), 'enterprise' (enterprise of a resident of a Contracting State), and the competent authority for each State. It provides that undefined terms are to be given the meaning they have under the domestic tax laws of the Contracting State applying the treaty provision, unless the treaty context requires otherwise.