(1):

(n.) The act of adopting, or state of being adopted; voluntary acceptance of a child of other parents to be the same as one's own child.

(2):

(n.) The choosing and making that to be one's own which originally was not so; acceptance; as, the adoption of opinions.

(3):

(n.) Admission to a more intimate relation; reception; as, the adoption of persons into hospitals or monasteries, or of one society into another.