Definitions determine treaty scope; undefined terms adopt the Contracting Party's domestic tax law or agreed common meaning. Article 4 defines core treaty terminology: territorial scope of 'India' and 'Samoa,' the 'Contracting Party' and competent authority, and taxable-unit terms such as 'person' and 'company.' It sets criteria for 'publicly traded company,' 'principal class of shares,' 'recognised stock exchange,' and defines 'collective investment fund or scheme,' 'tax,' 'information,' and 'information gathering measures.' Paragraph 2 specifies that undefined terms take their meaning from the domestic law of the relevant Contracting Party unless context or a mutual agreement of competent authorities under Article 11 provides otherwise.