NRI is a person who is a citizen of India or is a person of Indian origin or a foreign National of Indian Origin resident outside India for purposes of employment, carrying on business or vocation in circumstances as would indicate an intention to stay outside India for an indefinite period. An individual will also be considered NRI if his stay in India is less than 182 days during the preceding financial year.
PIO for this purpose is defined as a foreigner (not being a citizen of Pakistan, Bangladesh, Afghanistan, Iran, China, Sri Lanka, Nepal & Bhutan)
A foreign national, who was eligible to become citizen of India on26.01.1950 or was a citizen of India on or at any time after 26.01.1950 or belonged to a territory that became part of India after 15.08.1947 and his/her children and grandchildren, provided his/her country of citizenship allows dual citizenship in some form or other under the local laws, is eligible for registration as Overseas Citizen of India (OCI).