Definitions of deportation apply equally to nationals and foreigners. Nonetheless, in the common usage the expulsion of foreign nationals is usually called deportation, whereas the expulsion of nationals is called extradition, banishment, exile, or penal transportation. For example, in the United States:
"Strictly speaking, transportation, extradition, and deportation, although each has the effect of removing a person from the country, are different things, and have different purposes. Transportation is by way of punishment of one convicted of an offense against the laws of the country. Extradition is the surrender to another country of one accused of an offense against its laws, there to be tried, and, if found guilty, punished. Deportation is the removal of an alien out of the country, simply because his presence is deemed inconsistent with the public welfare and without any punishment being imposed or contemplated either under the laws of the country out of which he is sent or of those of the country to which he is taken."
Expulsion is an act by a public authority to remove a person or persons against his or her will from the territory of that state. A successful expulsion of a person by a country is called a deportation.
According to the European Court of Human Rights, collective expulsion is any measure compelling non-nationals, as a group, to leave a country, except where such a measure is taken on the basis of a reasonable and objective examination of the particular case of each individual non-national of the group. Mass expulsion may also occur when members of an ethnic group are sent out of a state regardless of nationality. Collective expulsion, or expulsion en masse, is prohibited by several instruments of international law.
Deportations widely occurred in ancient history.
Unlike in the Achaemenid and Sassanian periods, records of deportation are rare during the Arsacid Parthian period. One notable example was the deportaion of the Mards in Charax, near Rhages (Ray) by Phraates I. The 10,000 Roman prisonors of war after the Battle of Carrhae appear to have been deported to Alexandria Margiana (Merv) near the eastern border in 53 BC, who are said to married to local people. It is hypothesized that some of them founded the Chinese city of Li-Jien after becoming soldiers for the Hsiung-nu, but this is doubted.