Conventio

Lat. [from convenire, to come together.] In the civil law. A coming together of parties; a convention; an agreement. This was a term of the most general description, applying to all subjects upon which parties might come together for the purpose of entering into any engagement or transacting any business. Conventionis verbum generale est ad omnia pertinens de quibus negotii contrahendi transigendique causa consentiunt qui inter se agunt.

Dig. 2. 14. 1. 3.

It included the two leading divisions of contracts (contractus) and pacts (pacta).

Heinec.

El. Jur. Civ. lib.

3, tit. 14, § 784.