Adaptation of one ethnic or social group – usually a minority – to another. Assimilation involves the subsuming of language, traditions, values, mores
and behaviour or even fundamental vital interests.
Although the traditional cultural practices of the group are unlikely to be completely abandoned, on the whole assimilation will lead one group to be socially indistinguishable from other members of the society.
Assimilation is the most extreme form of acculturation.

Source: Glossary on migration.