Protestantism

from lat. “protestatio”, a statement issued by five reforming princes and 14 cities of the Holy Roman Empire at the Diet of Speyer in 1529; this was the first united declaration of faith of the reforming movement started by Martin Luther. In the 16th century there are many Protestant groups, their common denominators: salvation comes about by faith, and faith alone. The only authority are the Holy Scriptures of the Old and New Testament and the universal priesthood of all believers.

Source:

Cross, F.L., ed. The Oxford Dictionary of the Christian Church. Oxford: Oxford University Press, 1997.