An Amendment

1. An alteration or change for the better; correction of a fault or of faults; reformation of life by quitting vices.
2. In public bodies, any alteration made or proposed to be made in a bill or motion that adds, changes, substitutes, or omits.
3. (law) Correction of an error in a writ or process.
4. An addition to and/or alteration to the Constitution.
5. That which is added; that which is used to increase or supplement something.

improvement

reformation