adopti

Word lists gloss this as "to adopt (a child)" and stop, which loses half of it. Adopti has two settled senses and they are both formal: taking a child into the family in law, and a body formally accepting a proposal put before it. A committee adoptas rezolucion, a congress adoptas la tagordon, a parliament adoptas leĝon. Both senses share the shape of a deliberate decision with an official consequence.

What adopti does not cover is the loose English "adopt" for picking up a manner or a habit. That belongs to alpreni, which is al plus preni, to take on. Li alprenis seriozan mienon, he adopted a serious expression; ŝi alprenis la lokan kutimon, she adopted the local custom. Writing li adoptis seriozan mienon reads as though his face went through a court.

The family vocabulary derives normally: adoptito is the adopted child, adoptinto the person who adopted, and adoptaj gepatroj the adoptive parents. Adopto is the act, and both adopto and adoptado circulate, the second where you want the process rather than the single event.