Condign merit in Roman Catholic term designating the kind of goodness that is bestowed on a person because of the actions of that person.  It is merit.  It supposes equality between service and return.¹Catholic Encyclopedia, merit, newadvent.org/cathen/10202b.htm It is a reward for work accomplished only with the help of the Holy Spirit but it is actually a reward that is deserved.  If the reward is withheld due to condign merit, then there is injustice.

Condign merit (meritum de condigno) is contrasted with congruent merit which is the goodness bestowed on a person because of the work of another person, i.e., Jesus’ work on the cross bestows merit upon a person. If the reward is withheld due to congruent merit, then there is no injustice.

Strict merit is goodness bestowed as a contractual agreement between two or more parties.  An example would be getting paid money for work performed.

Summary of positions:  Condign merit (reward merit, not owed, but kindly given) the kind of goodness that is bestowed on a person because of the actions of that person. Congruent merit (merit from another) is the goodness bestowed on a person because of the work of another person. Strict merit (merit strictly due, as is a wage for work) is goodness bestowed as a contractual agreement between two or more parties.