naturalize

Concise Oxford English Dictionary © 2008 Oxford University Press:
naturalize /ˈnatʃrəlʌɪz/ (or naturalise)

▶verb

• 1 admit (a foreigner) to the citizenship of a country.

  ■ alter (an adopted foreign word) so that it conforms more closely to the phonology or orthography of the adopting language.

• 2 (usu. as adj. naturalized) Biology establish (a plant or animal) so that it lives wild in a region where it is not indigenous.

• 3 regard as or cause to appear natural.

  ■ explain (a phenomenon) in a naturalistic way.

– derivatives
naturalization noun.