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migration, of people, geographical movements of individuals or groups for the purpose of permanently resettling.

Early History

Migrations have occurred throughout history and have played an important part in the peopling of all the areas of the earth. Primitive migrations were usually in search of food, but could also result from physical changes, such as the advance of the continental ice sheets, and invasion by other peoples. The most important migrations in European history were the Gothic invasions (3d–6th cent.; see Germans), the Arab invasions (7th–8th cent.; see Arabs), the westward migration of the Golden Horde of Jenghiz Khan (13th cent.), and the invasions of the Ottoman Turks (14th–16th cent.; see Ottoman Empire; Turks).

Later Migrations

From the 17th to the 20th cent. migration involved individuals and families rather than nations or mass groups. The basic motive was economic pressure, as areas of low population density attracted people from high-density areas where economic opportunity was low. The desire for religious and political freedom has also been important, and national policies have played a part. In the largest international migration in history, c.65 million people migrated from Europe to North America and South America between the 17th cent. and World War II, while another 17 million went to Africa and Australia.

Nearly 12 million people, most from Mexico or Asia, migrated to the United States in the 1970s and 80s. Within the United States, migration patterns have traditionally been from east to west. Migration from north to south since the 1960s has resulted in the ascendancy of the Sun Belt, a region extending from Florida to S California. This trend has been supported by the southward migration of many blacks. Government regulation of migration became significant in the 20th cent. (see immigration).

Modern Migration Trends

Normal internal migration has been characterized by a population shift from rural to urban areas. In the United States, the portion of the population that lives in urban areas has risen steadily from 30% in 1910 to more than 70% in 1990; in Brazil, the percentage of urban dwellers has risen from 30% to 75% since 1940. Within urban areas, a large population shift from central cities to suburbs has occurred in the last half of the 20th cent. The development of totalitarianism and World War II resulted in a new pattern of forced mass migration within Europe. Over 30 million people were forcibly moved or scattered by the Nazis. In the postwar period c.10 million Germans and persons of German descent were forcibly expelled from Eastern Europe.

Other forced migrations since World War II have included the partitioning of India and Pakistan, which uprooted 18 million, and the establishment of the state of Israel, which created about one million refugees (see refugee). After the fall of Saigon (now Ho Chi Minh City) at the end of the Vietnam War in 1975, more than 600,000 fled Vietnam in the face of political persecution; many fled by boat and became known as the “boat people.” In South Africa, under the policies of apartheid, blacks were forced to live in designated “homelands” from 1959 to 1994. The Soviet invasion of Afghanistan in 1979 led to the migration of millions of Afghans to neighboring Pakistan and Iran.

In the 1980s and 90s war and civil strife continued to force massive refugee migration in many parts of the world. In Somalia and Ethiopia, civil war combined with long-term drought have resulted in large migrations of peoples (often from rural to urban areas and to neighboring countries) in an attempt to avoid famine. Hundreds of thousands of Kurdish refugees (see Kurds) have migrated from Iraq to Turkey and Iran in the wake of the civil war that followed the Persian Gulf War in 1991. The disintegration of Yugoslavia in the 1990s caused the dislocation of many peoples, especially Bosniaks, Croats, Serbs in areas other than Serbia, and Kosovars. In Rwanda and Burundi, millions of people, primarily Hutus, fled as ethnic civil war wrenched those nations in the mid-1990s; many of them fled to Zaïre (now Congo), where their presence aggravated civil and international strife.

The accelerating economic development in China that began in the 1990s led to an enormous migration from rural to urban areas, despite significant restrictions the Chinese government placed on changing residencies. Economic opportunity also has long been the major factor of the often illegal migration of individuals and families from Latin America into the United States, but political insecurity and violence has contributed as well, especially where Central America has been concerned. In Europe in the later 20th and early 21st cent., economic conditions have driven much of the migration to the continent from Africa, but conflict and political insecurity have also played a part. Conflict, however, was the dominant reason for the migration of hundreds of thousands from the Middle East, especially Syria, in the 2010s. Persecution and ethnic cleansing in 2017 against Muslim Rohingya in mainly Buddhist Myanmar resulted in the influx of hundreds of thousands of refugees into neighboring Bangladesh.

In 2018, following a 2016 declaration on international migration by the United Nations, 150 nations signed the Global Compact for Safe, Orderly, and Regular Migration. Affirming that migrants no matter what their status have human rights, the compact sought to improve access to basic services, eliminate discrimination and safeguard working conditions, improve antismuggling and antitrafficking measures and efforts, and provide for a safe, dignified repatriation. Although the compact was nonbinding, a number of nations including the United States, Australia, and several East European nations rejected the compact.


See A. A. Brown and E. Neuberger, Internal Migration (1977); M. Greenwood, Migration and Economic Growth in the United States (1981); G. J. Lewis, Human Migration (1982); W. Weidlich and G. Haag, ed., Interregional Migration (1988); R. King, ed. Atlas of Human Migration (2007) and as author, People on the Move: An Atlas of Migration (2010); I Goldin et al., Exceptional People: How Migration Shaped Our World and Will Define Our Future (2011).

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the movement of people from one country to another, involving an intention to reside in the country of destination. Emigration refers to the movement out of a country, immigration refers to the movement of people into a country. There is an internationally agreed definition of an immigrant as someone who, having lived outside the country for at least one year, declares an intention to live in the country for at least one year. An emigrant is defined in the opposite way Since World War II more people have emigrated from the UK than immigrated into it. In recent British history there have been three periods of marked immigration: Irish people 1800-61; Jewish people 1870-1911; and people from the New Commonwealth 1950-71. There have been a number of MORAL PANICS about immigration since 1945, focusing on the immigration of black people, and it is therefore important to distinguish between immigrants and black people; it is wrong to assume that an immigrant is black, and it is equally wrong to assume that a black person is an immigrant. See also LABOUR MIGRATION, ETHNIC GROUP, RACISM OR RACIALISM.
Collins Dictionary of Sociology, 3rd ed. © HarperCollins Publishers 2000


The movement of an atom or group of atoms to new positions during the course of a molecular rearrangement.
(chemical engineering)
(computer science)
Movement of frequently used data items to more accessible storage locations, and of infrequently used data items to less accessible locations.
The transfer of genetic information among populations by the movement of individuals or groups of individuals from one population into another.
Movement of a topographic feature from one place to another, especially movement of a dune by wind action.
Movement of liquid or gaseous hydrocarbons from their source into reservoir rocks.
Slow, downstream movement of a system of meanders.
The uncontrolled movement of certain metals, particularly silver, from one location to another, usually with associated undesirable effects such as oxidation or corrosion.
(solid-state physics)
The movement of charges through a semiconductor material by diffusion or drift of charge carriers or ionized atoms.
The movement of crystal defects through a semiconductor crystal under the influence of high temperature, strain, or a continuously applied electric field.
(vertebrate zoology)
Periodic movement of animals to new areas or habitats.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


The spreading or creeping of a sealant onto adjacent surfaces, usually to the detriment of bond.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.


To move data or software from one location to another. Migration often means "copy" as much as it does "move." For example, "let's migrate our photos from the computer to the tablet" does not necessarily connote the photos are deleted from the computer after the transfer. Following are the various kinds of migration that take place in the computer world.

Storage Migration
Moving data from one storage system to another for efficiency, backup or archiving. Also called "data migration." See HSM.

Application Migration
Moving application programs from one computer to another. See PC migration.

Data Migration
Moving data from a computer, tablet or smartphone to another device. See PC migration.

Domain Migration
Moving a website or other Internet-based service from one ISP to another or from one server to another. See Internet domain name.

Cloud Migration
Moving an in-house system to the cloud. See cloud computing.
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