Affinity is a word used in Catholic Canon Law to describe the relationship between two people that used to be married to each other. This law says that if two people were married, then later on, one of them gets married to someone else, then the two people who were married to each other will still be related to each other kind of like a family. This means that the two people who were married to each other before are not allowed to marry each other again, because it would make them too close. It would be like a brother and sister getting married. That's not allowed.