[F]orm of Christian faith and practice that originated with the principles of the Reformation.
Protestantism as a general term is now used in contradistinction to the other major Christian faiths, Roman Catholicism and Eastern Orthodoxy.
Two distinct branches of Protestantism grew out of the Reformation. The evangelical churches in Germany and Scandinavia were followers of Martin Luther, and the reformed churches in other countries were followers of John Calvin and Huldreich Zwingli. A third major branch, episcopacy, developed in England. Particularly since the Oxford movement of the 19th cent., many Anglicans have rejected the word Protestant because they tend to agree with Roman Catholicism on most doctrinal points, rejecting, however, the primacy of the pope (...) In addition, there have been several groups commonly called Protestant but historically preceding the rise of Protestantism (...).
The doctrine that the individual conscience is the valid interpreter of Scripture led to a wide variety of Protestant sects; this fragmentation was further extended by doctrinal disputes within the sects notably over grace, predestination, and the sacraments.
The chief characteristics of original Protestantism were the acceptance of the Bible as the only source of infallible revealed truth, the belief in the universal priesthood of all believers, and the doctrine that a Christian is justified in his relationship to God by faith alone, not by good works or dispensations of the church. There was a tendency to minimize liturgy and to stress preaching by the ministry and the reading of the Bible.
Protestantism saw many theological developments, particularly after the 18th cent. Under the influence of romanticism, which stressed the subjective element in religion rather than the revelation of the Bible, the formal systems of early Protestant theology began to dissolve; this doctrine was best expressed by Friedrich Schleiermacher, who placed religious feeling at the center of Christian life. Along with this came the assertion that the fatherhood of God and the unity of humanity were the basic themes of Christianity. Later there was a neoorthodox movement, which, under the leadership of Karl Barth and Reinhold Niebuhr, sought a return to a theology of revelation; a new school of Bible interpretation as expressed in the work of Rudolf Bultmann; and a theology, derived in part from existentialism, developed by Paul Tillich.
In the United States, four broad theological positions cut across denominational lines: fundamentalism, which stems from the antitheological periods of revivalism in the 18th and 19th cent. (see Great Awakening) and adheres to a literal interpretation of the Bible and a pietistic morality; liberalism, the heir to the Social Gospel movement, which encourages freer interpretation of theological doctrines and emphasizes church responsibility for social justice; Pentecostalism, which emphasizes ecstatic religious experience especially as communicated through the gifts of the Spirit; and the neoorthodoxy of Reinhold Niebuhr and Karl Barth.
Protestantism, The Columbia Encyclopedia, Sixth Edition
[O]ne of the three major branches of Christianity, originating in the 16th-century Reformation. Its original basic doctrines, in addition to those of the creeds, were: justification by grace alone through faith alone; the priesthood of all believers; the supremacy of Holy Scripture in matters of faith and order. There has been variation in sacramental doctrine among Protestants, but the limitation of the number to the two ''sacraments of the Gospel,'' baptism and Holy Communion, has been almost universal.
Within the spectrum of non-Roman Catholic Western Christianity a great variety of doctrinal views and polities have been expressed. Not all Western non-Roman Catholic Christians have been ready to be included in Protestantism. Some Anglicans and Lutherans, for instance, have been so eager to stress their continuity with the historic Roman Catholic Church and their distance from extreme Protestantism that they have asked for separate designations. Courtesy suggests that such appeals be taken seriously; however, ultimately habits of speech and sociological usage tend to predominate and, despite their protestations, these groups are usually included in the Protestant cluster.
Protestantism, Encyclopedia Britannica
» Protestantism Entry in the Encyclopedia Britannica