adoptive parent vs adopter

adoptive parent and adopter both are nouns.

Word	Noun	Adjective	Verb	Adverb
adoptive parent	Yes	No	No	No
adopter	Yes	No	No	No

As nouns, adoptive parent and adopter are synonyms defined as:

adoptive parent and adopter: a person who adopts a child of other parents as his or her own child

adoptive parent (noun)	adopter (noun)
a person who adopts a child of other parents as his or her own child	a person who adopts a child of other parents as his or her own child