Non Resident Indian (NRI) is a citizen of Indian, who remains overseas for employment/carrying on business or profession outside Indian or remains overseas under circumstances showing an intention for an uncertain duration of stay overseas is a non-resident. Non-resident foreign citizens of Indian Origin are treated at par with Non Resident Indian (NRIs).

Person of Indian Origin (PIO) (not being a citizen of Pakistan or Bangladesh or Sri Lanka or Afghanistan or China or Iran or Nepal or Bhutan), who –  At any time, held Indian passport, or – Who or either of whose father or whose grandfather was a citizen of India by virtue of the Constitution of India or the Citizenship Act, 1955 (57 of 1955).

Any person of full age and capacity :
Who is a citizen of a different country, but was a citizen of India at the time of, or at any time after, the beginning of the constitution, or
Who is a citizen of another country, but was qualified to become a citizen of India at the time of the commencement of the constitution, or
Who is a citizen of another country, but belongs to a area that became part of India after the 15th Day of August, 1947. Who is a child of such a citizen, or

A person, who is minor child of a person mentioned in previous clause:
Provided that no person, who is or had been a citizen of Pakistan, Bangladesh shall be capable for signing up as an Overseas Citizen of India.