What is diaspora? What is expatriate? What is immigrant? What is nationality? What is assimilation? What is identity? What is hybridity?
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These are pretty much standard terms in postcolonial theory and some of these terms have very specific meanings in that field of theory. I would encourage you to look for specific resources on postcolonialism for fuller definitions.
Diaspora, for example, is often used to talk about the mass migration (most often completely involuntary, in the form of chattel slavery) of Africans across the Pacific Ocean.
Similarly, expatriate often means more than simply someone who lives in a country that she or he wasn't born in; the term is often used for someone who has moved out of a sense of dissatisfaction or protest and who maintains uneasy, conflicted ties to the home country.
Hybridity is one of my favorite terms because it captures so well the sense of what happens when very different cultures meet and people grow up in the overlapping spaces (such as is especially easy to see in border towns or in multi-generational immigrant families). "Hybrid" was intially a term in biology, I believe, but has expanded its meaning to talk about developments in culture.
Diaspora -- the people from a country who have left that country and spread out in the outside world. Ex: Jewish diaspora from Israel to Europe and America.
Expatriate -- someone from one country living in another
Immigrant -- term for a person in a given country who has moved to that country from another country.
Assimilation -- the process of bringing non-native people into a country's native culture -- making the newcomers be like the natives.
Identity -- the way in which people identify themselves with one country or ethnic group or another.