What term is used for the legal adoption of one paterfamilias by another that requires formal approval?

The term "adrogatio" refers specifically to the legal adoption of one paterfamilias by another in ancient Roman law, which necessitates formal approval from the state. This process was distinct because it involved the full submission of one family's authority to another, requiring the endorsement of a magistrate. Adrogatio was typically reserved for exceptional cases, such as when the adopted head of the family had no male heirs or needed to ensure the continuity of the family line and its assets.

In contrast, "adoptio" refers to a more common form of adoption, happening within non-paterfamilias contexts, where a person could be adopted into a family but did not necessarily require the same formal state oversight. "Sui iuris" refers to the legal status of being independent and having full legal rights, while "emancipatio" is the process of freeing a son from the authority of the father, allowing him to become his own legal representative. Thus, adrogatio is the correct term when discussing the formal legal process of adopting a paterfamilias.