Acculturation is the process of systematic cultural change of a particular society carried out by an alien, dominant society. Alfred Kroeber stated that acculturation consists of  those changes in one culture brought about by contact with another culture, resulting  in an increased similarity between the two cultures.

Kroeber (1948) described acculturation as changes produced in a culture because of the influence of another culture, with the two cultures becoming similar as the end result.

The Encyclopedia of Social and Cultural Anthropology (1996) defines acculturation as the process of acquiring culture traits as a result of contact and that it was a common term, especially used by American anthropologists.

The most profound changes in a society result from direct, aggressive contact of one society with another. There is hardly any modern society which has not felt the impact of this contact with very different societies. The process of the intermingling of cultures is called acculturation. Because the influence of Euro-American culture on nonliterate, relatively isolated groups has been so widespread and profound, the term acculturation is most commonly applied to contact and intermingling between these two cultures.

The change may be reciprocal, however, very often the process is asymmetrical and the result is the (usually partial) absorption of one culture into the other. The change is brought about under conditions of direct contact between individuals of each society. The process results in the two cultures becoming similar, or one-way and may result in the extinction of one culture, when it is absorbed by the other. Acculturation contrasts with diffusion of culture traits in that it is a process of systematic cultural transformation of individuals in a society due to the presence on an alien, politically dominant society .

Kroeber believed that acculturation is gradual rather than abrupt.

Kroeber connected the process of diffusion with the process of acculturation by considering that diffusion contributes to acculturation and that acculturation necessarily involves diffusion.

Diffusion is a matter of what happens to the elements of a culture; whereas acculturation is a process of what happens to a whole culture.

Individuals of a foreign or minority culture learn the language, habits, and values of a standard or dominant culture by the cultural process of acculturation.

The process by which individuals enter the social positions, as well as acquire the political, economic, and educational standard,s of the dominant culture is called assimilation. These individuals, through the social process of assimilation, become integrated into the “standard” culture .

Milton Gordon  proposed that assimilation can be described as a series of stages through which an individual must pass. These three stages are behavioral assimilation (acculturation), structural assimilation (social assimilation), and marital assimilation of the individuals of the minority society and individuals of the dominant society. Acculturation is the first stage in the series, not all individuals go past this stage. It is not always possible to adopt the dominant culture’s way of life completely, in order to assimilate Although this proposal has been criticized, it does indicate that there is a continuum through which individuals pass, beginning with acculturation and ending with complete assimilation.

Complete assimilation is not the inevitable consequence of acculturation due to the value systems of the minority or weaker culture being a part of the entire configuration of culture. It may not always be possible, nor desirable, for the minority culture to take over the complete way of life of the majority culture. Often a period of transition follows where the minority society increasingly loses faith in its own traditional values, but is unable to adopt the values of the dominant culture. During this transition period there is a feeling of dysphoria, in which individuals in the minority society exhibit feelings of insecurity and unhappiness.

Acculturation and assimilation have most often been studied in European immigrants coming to the United States during the nineteenth and early twentieth centuries, as well as minority groups already living in the United States. European “white ethnics” have experienced a higher rate of assimilation than nonwhite, non-European, and more recently immigrated groups.

These studies have resulted in several important cross-cultural generalizations about the process of acculturation and assimilation. According to Thompson (1996), these generalizations are as follows:

1. Dominant cultures coerce minorities and foreigners to acculturate and assimilate. This process is slowed down considerably when minorities are territorially or occupationally concentrated, such as in the case of large native minorities who often become ethnonationalistic.
2. Acculturation must precede assimilation.
3. Even though a minority may be acculturated, assimilation is not always the end result.
4. Acculturation and assimilation serve to homogenize the minority group into the dominant group. The many factors facilitating or preventing this homogenization include the age of the individual, ethnic background, religious and political affiliations, and economic level .

An individual is assimilated when he is capable of entering social positions and political, economic, and educational areas of the standard society. If he cannot, he may simply remain acculturated because he has learned the language, habits, and values of the standard or dominant culture.

Acculturation studies evolved into assimilation studies during the late nineteenth century and early twentieth centuries when great numbers of immigrants arrived in the United States. Studies of the rate of assimilation of minority groups already living in the United States became another area of focus. The pursuit of explanations for why different groups assimilate at different rates have largely guided many acculturation and assimilation studies .