出典:国際連合
The population of a sovereign country (305-3) may be involved in internal migration 1 when both place of departure (801-4) and place of destination (801-5) are within the country, or in international migration 2 which occurs across national boundaries. The term external migration 3 is sometimes encountered in the latter sense. International migration is called immigration 4 or emigration 5 according to whether the country in question is the country of destination or the country of origin. When the country is divided into sub-areas, movement within the boundaries of each sub-area are local moves 6 and constitute residential mobility 6, while movement between sub-areas is called in-migration 7 or out-migration 8 depending on whether the sub-area considered is the place of destination or the place of origin for the migrants. A migration stream 9 is a group of migrants having a common origin and destination. The larger stream between two sub-areas is called the dominant stream 10 and the smaller the counterstream 11.