Lack of assimilation perpetuates ethnic and social differences and discrimination, and makes conflict more likely. It also leaves the way open for subversive activities or foreign intervention to protect an oppressed group. Assimilation involves the adoption of 'national' characteristics by different racial and ethnic groups and the elimination of racial and ethnic differences in the social structure, which may be very difficult to achieve and not desirable in so far as it involves a loss of cultural heritage.
Lack of assimilation may occur wherever there are minority groupings of a racial, religious, ideological or linguistic kind. The groups may be immigrant or indigenous. It is aggravated by social inequalities and exploitation which create ethnic conflict. Since ethnic differences may be very great, assimilation means that at least one group must give up some of its customs, which it may be very unwilling to do. Where there is extensive segregation and little intermarriage, ethnic purity is likely to remain intact and prejudices and discrimination persist.