What is the term for formal engagement in Roman marriage customs?

The term for formal engagement in Roman marriage customs is "Sponsalia." In ancient Roman culture, sponsalia referred to the formal betrothal process that involved an agreement (often formalized through a contract) between the families of the bride and groom. This engagement was a significant step in the process of marriage and included various ceremonies and customs that marked the commitment of the couple to one another, often leading to the subsequent marriage ceremony.

Usus is another aspect of Roman marriage, related to cohabitation and informal partnerships, but it does not specifically refer to the engagement process. Bulla refers to a charm or amulet worn by Roman children, primarily boys, which does not pertain to marriage customs. Tunica recta is the ceremonial garment worn by a bride during the wedding ceremony, which occurs after the engagement has taken place. Thus, the correct term that signifies the formal engagement phase within Roman marriage traditions is indeed Sponsalia.