Reformation
Reformation is the general term for the period of massive ecclesial and theological change in Western Christianity that had its roots as early as the fourteenth century and lasted into the seventeenth century. The Reformation refers more specifically to the break with medieval Roman Catholicism launched in the sixteenth century by such luminaries as Martin Luther, Ulrich Zwingli and John Calvin, who protested against what they perceived as the overall degeneracy of the Roman Church and its departure from what the Reformers saw as the faith of the apostles and early church fathers (Stanley J. Grenz, David Guretzki, and Cherith Fee Nordling. Pocket Dictionary of Theological Terms).