A more thorough explanation:

Definition: Affinitas (ə-fɪnə-təs) is a Latin term used in Roman law to refer to the relationship by marriage.

Example: If John marries Mary, then John's affinitas will include Mary's family members, such as her parents, siblings, and other relatives by marriage.

Explanation: Affinitas is a legal term that describes the relationship between two families that are joined by marriage. In the example given, John's affinitas will include Mary's family members because they are now related by marriage. This term is important in Roman law because it determines the legal rights and obligations of the families involved.