As nouns the difference between reparation and reformation
is that reparation
is a payment of time, effort or money to undo past transgression(s) while reformation
is an improvement (or an intended improvement) in the existing form or condition of institutions or practices etc.; intended to make a striking change for the better in social or political or religious affairs.
As a proper noun Reformation is
the religious movement initiated by Martin Luther
in the 16th century to reform the Roman Catholic Church.