An expatriate (in abbreviated form, expat) is a person temporarily or permanently residing in a country and culture other than that of the person’s upbringing. The word comes from the Latin terms ex (“out of”) and patria (“country, fatherland”).

In its broadest sense, an expatriate is any person living in a different country from where he or she is a citizen. In common usage, the term is often used in the context of professionals sent abroad by their companies, as opposed to locally hired staff. The differentiation found in common usage usually comes down to socio-economic factors, so skilled professionals working in another country are described as expatriates, whereas a manual labourer who has moved to another country to earn more money might be labelled an ‘immigrant’. There is no set definition and usage does vary depending on context and individual preferences and prejudices. ‘Expatriation’ has also been used in a legal sense to mean ‘renunciation of allegiance;’ the Expatriation Act of 1868 said in its preamble, ‘the right of expatriation is a natural and inherent right of all people, indispensable to the enjoyment of the rights of life, liberty and the pursuit of happiness.’

In the 19th century, Americans, numbering perhaps in the thousands, were drawn to Europe—especially to Munich and Paris—to study the art of painting. Henry James, for instance, was a famous expatriate American writer from the 1870s, who adopted England as his home.

The term ‘expatriate’ in some countries also has a legal context used for tax purposes. An expatriate living in a country can receive a favourable tax treatment. In this context a person can only be an expatriate if they move to a country other than their own to work with the intent of returning to their home country within a certain period. The number of years can vary per tax jurisdiction, but 5 years is the most commonly used maximum period. If you are not affected by taxes 3 years is normally the maximum time spent in one country.[clarification needed]
During the Nazi era, the German government deprived many left-wing and intellectual opponents of citizenship through expatriation, such as Albert Einstein, Oskar Maria Graf, Willy Brandt and Thomas Mann, often expatriating entire families.

Courtesy: Wikipedia