reformation

Short definition from Wiktionary

Noun

1. 1
   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, political or religious affairs or in the conduct of persons or operation of organizations.
2. 2
   Change or correction, by a court in equity, to a written instrument to conform to the original intention of the parties.
3. 3
   Alternative form of re-formation.

Proper noun

1. 1
   The religious movement initiated in the 16th century against the Roman Catholic Church.