In Roman Catholicism, strict merit is goodness bestowed on a person that is directly due to the person's work. An example would be a contractural agreement between two or more parties where a peron would get paid money for work performed.
Summary of positions: Condign merit is the kind of goodness that is bestowed on a person because of the actions of that person. It is not owed but is kindly given. If the reward is withheld, then that is not just. Congruent merit (merit from another) is the goodness bestowed on a person because of the work of another person. If the reward is withheld, there is no injustice. Strict merit (merit strictly due, as is a wage for work) is goodness bestowed as a contractural agreement between two or more parties. If not given, it is not just.