'''同化'''或'''同化政策'''在社會學上是指個人或團體，被融入非原本，但具社會支配地位的民族傳統文化的過程。同化原本是生物學的概念（参见同化 (生物学)），後來被社會學借用。

==同化定義==
被同化者通常是外地來的移民或少數民族。由于生活在非原本社會中或與其接觸，慢慢失去大部份原來的文化特點；並接受非原本社會的特點。變化直到與非原本社會的成員無法區分為止。

同化並不指種族上或其他生理上的融合，雖然這種融合與同化有莫大關聯。 

==世界各地的同化情況==
有學者認為徹底同化很少見，以歐洲為例，雖然當地各民族歷經多次被征服及強制同化，但卻沒有因此融為一體，反而分化出更多民族。

而比較值得注意的同化例子是美國，例如美國的黑人，多数原是來自非洲的黑奴，現在極大多數已忘却本身文化；另外移民美國的歐洲各國人也多數在兩三代內幾乎完全被同化。

其實同化最成功的例子是中國，中國的面積與整個歐洲差不遠，但達至統一卻有很長歷史。

秦始皇于公元前221年統一中國後，下令書同文，命李斯依據周朝的大篆，编成小篆，通行全國，原本有不同文字的六國遺民被同化；而後秦朝继续擴張版圖，征服了陸梁地，遂定南越，以為桂林、南海、象等三郡，即今天的福建、廣東、廣西等地，當地原居住着異民族，但而後完全被同化成漢族。

'''Cultural assimilation''' (often called merely ''assimilation'') is a process of integration whereby members of an ethno-cultural community (such as immigrants, or ethnic minorities) are "absorbed" into another, generally larger, community. This implies the loss of the characteristics of the absorbed group, such as language, customs, ethnicity and self-identity. 

Assimilation may be voluntary or forced, as is often the case regarding ethnic minorities (see forced assimilation).

A region or society where several different groups are spontaneously assimilated is sometimes referred to as a melting pot.

== Cultural influence ==
A group (a state or an ethnicity) can spontaneously adopt a different culture due to its political relevance,  or to its perceived superiority. The first is the case of the Latin culture and language, that were gradually adopted by most of the subjugated people. 

The second is the case of subjugated, but older and richer culture, which see itself imitated by the new masters, e.g. the victorious Roman Republic adopted more from the Hellenistic cultures than it imposed in most domains, except such Roman specialities as law and the military.

== Assimilation of immigrants ==

Immigrant assimilation is a complex process in which an immigrant fully integrates themselves into a new country. Social scientists rely on four primary benchmarks to assess immigrant assimilation: socioeconomic status, geographic distribution, second language attainment, and intermarriage.  William A.V. Clark defines immigrant assimilation "as a way of understanding the social dynamics of American society and that it is the process that occurs spontaneously and often unintended in the course of interaction between majority and minority groups".<ref name="Clark">Clark, W. 2003 Immigrants and the American Dream Remaking the Middle Class. NY, NY: The Guilford Press.</ref>.

It has been found that between 1880 and 1920, the United States took in roughly 24 million immigrants.<ref name="Waters">Waters, Mary C.; Jiménez, Tomás R. "Assessing Immigrant Assimilation: New Empirical and Theoretical Challenges" Annual Review of Sociology, Vol. 31 No. 1 (2005) 105-125</ref>  This increase in immigration can be attributed to many historical changes. Later, during the cold war from the 1960s through the 1980s and the disintegration of the Soviet Union in the late 1980s,<ref name="Googlebook">[http://books.google.com/books?id=QfgeSqbznVUC&pg=PA230&dq=cold+war+politics+from+the+1960s+through+the+1980s+disintegration+of+the+soviet+union+in+the+late+1980s&sig=D9dLrIZ_je3y-5FO8IOBwvEADHI#PPA232,M1].</ref> over 1.8 million Jews (including some non-Jewish family members) emigrated from the former Soviet Union.<ref name="Googlebook"/> The major destination countries were Israel (about 1.1 million), the United States (over 400,000), Germany (about 130,000), and Canada (about 30,000).<ref name="Googlebook"/> The beginnng of the twenty-first century has also marked a massive era of immigration, and sociologist are once trying to make sense of the impact that immigration has on society and the impact it has on immigrants themselves.<ref name="Waters"/>

==== Theoretical explanations ====

Researchers have attempted to explain the assimilation rate for post 1965 immigrants in the United States with experiences of immigrants who entered the United States between 1880 and 1920.<ref name="Waters"/> Many of the methods and theories that are used to assess immigrant assimilation today are derived from earlier immigrant studies.  One of the leading theories in understanding immigrant assimilation came from William I. Thomas and Florian Znaniecki whom published "The Polish Peasant in Europe and America".<ref name="Waters"/> William I. Thomas and Florian Znaniecki's study on Polish immigrants(1880-1910)assessed how these immigrants built an institutional community in the United States during the Napoleonic War.[http://books.google.com/books?id=HOLITuv6UvkC&dq=the+polish+peasant+in+europe+and+america&pg=PP1&ots=FaFVA_ub6r&sig=bSaxdvnKBqVIbBRlP5G1_5ijMT0&hl=en&prev=http://www.google.com/searchhl=en&rlz=1G1GGLQ_ENUS254&q=the+polish+peasant+in+europe+and+america&btnG=Search&sa=X&oi=print&ct=title&cad=one-book-with-thumbnail]  Another influence on immigrant assimilation came from Robert Park, Ernest Burgess, and William I. Thomas, in which they trained graduate students to study the experiences of immigrants in Chicago.  Robert Park, Ernest Burgess, and William I. Thomas provided these graduate students with theoretical tools such as Park's theory on collective behavior.<ref name="Waters"/> The third theory on immigrant assimilation comes from Gordon's book, Assimilation in American life.  Gordon highlighted the generational change in immigrant groups, it states that the first generation or foreign born were less assimilated and less exposed to American life than their American-born children (the [second generation]), and their grandchildren (third-generation) were more like the American mainstream than their parents.<ref name="Waters"/>.

====Theoretical models to immigrant assimilation====

The first, classic and new assimilation model sees immigrants and native-born people following a "straight-line" or a convergence.[http://www.migrationinformation.org/feature/display.cfm?id=442] This theory sees immigrants becoming more similar over time in norms, values, behaviors, and characteristics.[http://www.migrationinformation.org/feature/display.cfm?id=442] This theory also expects those immigrants residing the longest in the host population, as well as the members of later generations, to show greater similarities with the majority group than immigrants who have spent less time in the host society.[http://www.migrationinformation.org/feature/display.cfm?id=442]The second, [racial]/ethnic disadvantage model states that immigrant's chances to assimilate are "blocked". An example of this model would be discrimination and institutional barriers to employment and other opportunities.[http://www.migrationinformation.org/feature/display.cfm?id=442]. The third, the segmented assimilation model theorizes that structural barriers, such as poor urban schools, cut off access to employment and other opportunities — obstacles that often are particularly severe in the case of the most disadvantaged members of immigrant groups, and such impediments can lead to stagnant or downward mobility, even as the children of other immigrants follow divergent paths toward classic straight-line assimilation. [http://www.migrationinformation.org/feature/display.cfm?id=442].

==== Core measurements to immigrant assimilation ====

Researchers have assessed that assimilation exists among immigrants because we can measure assimilation on four primary benchmarks. These core measurable aspects of immigrant assimilation that were formulated to study European immigrants are still the starting points for understanding current immigrant assimilation. These measurable aspects of assimilation are socioeconomic status, spatial concentration, language attainment, and intermarriage.<ref name="Waters"/>

#''Socioeconomic Status'' is defined by educational attainment, occupation, and income. By measuring socioeconomic status researchers want to find out if immigrants eventually catch up to native-born people in terms of human capital characteristics. 
#''Spatial Concentration'' is defined by geography or residential patterns. The spatial residential model (based on theories of Park) proposed by Massey states that increasing socioeconomic attainment, longer residence in the U.S, and higher generational status lead to decreasing residential concentration for a particular ethnic group.<ref>Ellis, Mark and Goodwin-White, J. "Generation Internal Migration in the U.S.: Dispersion from States of Immigration?" International Migration Review, Vol. 40 No. 4 (2006) 899-926 </ref>.
#''Language Attainment'' is defined as the ability to speak English and the loss of the individual's mother tongue.<ref name="Waters"/> The three-generation model of language assimilation states that the first generation makes some progress in language assimilation but remains dominant in their native tongue, the second generation is bilingual, and the third-generation only speaks English.<ref name="Waters"/>
#''Intermarriage'' is  defined by race and only occasionally by ethnicity and generation.<ref name="Waters"/> High rates of intermarriage are considered to be an indication of social integration because it reveals intimate and profound relations between people of different groups, intermarriage reduces the ability of families to pass on to their children a consistent ethnic culture and thus is an agent of assimilation.<ref>Pagnini, L. and Morgan, S.P. "Intermarriage and the social distance among U.S. Immigrants at the Turn of the Century" American Journal of Sociology, Vol 96 No.2 (1990) 405-432.</ref>

====Policies on immigrant assimilation====

When considering immigrant assimilation it is important to consider why immigrants migrate. One reason immigrants migrated was The 1986 Immigration Reform and Control Act(IRCA), which legalized 2.3 million formally undocumented Mexican Immigrants.<ref name="Waters"/> This Act freed these newly legalized immigrants from the fear of being apprehended, and it was found that many of these immigrants moved to states beyond the nearest U.S-Mexican border.<ref name="Waters"/>.