Calvinism -
the theological system of John Calvin and his followers emphasizing omnipotence of God and salvation by grace alone
protestantism the theological system of any of the churches of western Christendom that separated from the Roman Catholic Church during the Reformation
Calvinism (also called the Reformed tradition, the Reformed faith, or Reformed theology) is a theological system and an approach to the Christian life. The Reformed tradition was advanced by several theologians such as Martin Bucer, Heinrich Bullinger, Peter Martyr Vermigli, and Huldrych Zwingli, but this branch of Christianity bears the name of the French reformer John Calvin (or Jean Cauvin in the old French) because of his prominent influence on it and because of his role in the confessional and ecclesiastical debates throughout the 16th century. Today, this term also refers to the doctrines and practices of the Reformed churches of which Calvin was an early leader.
