assimilation n.

early 15c., in physiology, "absorb into and make part of the body," from Latin assimilatus, past participle of assimilare, assimulare "to make like, copy, imitate, assume the form of; feign, pretend," from assimilated form of ad "to" (see ad-) + simulare "make similar," from similis "like, resembling, of the same kind" (see similar).

The meaning "make alike, cause to resemble," and the intransitive sense "become incorporated into" are from 1620s. In linguistics, "bring into accordance or agreement in speech," from 1854. Related: Assimilated; assimilating.

"one who advocates racial or ethnic integration," 1900, originally in reference to Hawaii and possessions obtained by the U.S. in the war against Spain; later with reference to Jews in European nations; see assimilation + -ist. In Portuguese, assimilado (literally "assimilated," past participle of assimilar) was used as a noun of natives of the Portuguese colonies in Africa who were admitted to equal rights and citizenship.

also mal-assimilation, "faulty digestion, imperfect nutrition," 1840, from mal- + assimilation.