The word Diaspora as defined by the Oxford English dictionary means the scattering or moving away of a people from their original homeland or country. The word Diaspora is of Greek origin and was originally applied to the scattering of the Jews from ancient Israel. The word diaspora has been since used to describe the movement or migration or even scattering of a people beyond the borders of their original country. The Indian Diaspora describes the movement of Indians from India to other parts of the world. The Indian Diaspora should be seen from the span of history and categorisation into movements at each aspect of history.
We can begin with the oldest known Indian diaspora, arguably, into the Bronze Age, 3,000 to 4,000, years ago, when traders from the Harappan civilization moved to Sumerian and Akkadian cities in what is now Iraq as well as to Oman and what are now the Gulf States.
The next well known Indian Diaspora, and the usual focus of interest in the study of the Indian Diaspora, stems directly from British colonization when between the 1800s and 1900s saw the movements of Indians to various parts of the expansive British Empire.
Then we have the relatively recent movement of Indians to the west from the 1970s onwards. This diaspora saw the benefits America, especially, derived from highly qualified and talented Indians delving into the growing IT industry as well into the medical, engineering and scientific fields. All this lending to Americas greatness.
There is evidence of smaller, lesser known migrations. There was a migration of Indians from the state of Kerala, in south west India, to what became Jaffna in Sri Lanka. There was a migration of Indians during the Chola kingdom to the Malay Archipelago, into what is now Malaysia and Indonesia. From there, these Indians moved to Cambodia where they created a civilisation that saw the construction of the Angkor Wat temple complex. The Dutch in the 1600s sent Indians as well as Indonesians to what is now South Africa, the migration of Punjabis to the United States in the early 1900s. In the 1600s Dutch traders sent Indians to that part of Africa.
When Uganda, Kenya and Fiji saw nationalist parties enter mainstream politics in those countries there was a migration out of those countries by Indians to Britain, Australia, New Zealand, Canada and the USA.
However the most well-known Indian Diaspora is the product of British colonisation of India and the migration to America and Europe from the 1970s. These two episodes in the history of our venerable, ancient mother country are Diasporas that are mostly studied.
Having said all that. Emigration from the motherland or from other countries such as in Africa, has had various results. In the case of the recent emigration to America has seen accomplishments by highly educated and talented people contributing to America at the expense of India. What is happening is that acculturation is taking place among the children of Indian emigrees into Western culture and their shunning of Indian culture. There are cases of adult emigrees who refuse to acknowledge their Indian roots and culture. It was noted that the later American astronaut, Kalpana Chawla, who was married to a Frenchman, told a young girl from India not to call her "Didi" which is Hindi for sister. That woman's outlook was western. It must be noted that she was born and educated in mother India. An ungrateful wretch. She shied away from anything Indian. There are young Indians who went along with their parents to western countries or were born there who are fast adopting western values and shying away from Indian values. These are such as sexual promiscuity, intermarriage, religious conversion, partying late into the night, etc.