1.  adoptive(a = adj.all) - of parents and children; related by adoption; "adoptive parents"
Antonym: biological
Derived form verb adopt₅

2.  adoptive(a = adj.all) adopted - acquired as your own by free choice; "my adopted state"; "an adoptive country"
Derived form verb adopt₂

   Pertaining to adoption; made or acquired by adoption; fitted to adopt; as, an adoptive father, an child; an adoptive language. [1913 Webster]

adoptive, adj. due to adoption (adoptive son; adoptive father).

Derivative:
adoptively adv.

Etymology:
ME f. OF adoptif -ive f. L adoptivus (as ADOPT)

adoptive parent