A simple definition based in doctrine, history, or sociology won’t do. But a vibrant stream really does exist.
Evangelicalism is one of the largest and most dynamic forms of Christianity in the modern world, but there is an amorphous quality to many words that end with the suffix “-ism,” and “evangelicalism” is no exception. “Evangelicalism” does not have the hard and crisp denotation of a concrete noun such as “Jesuit.” This confusion goes back to lexical roots. The English language uses the Anglo-Saxon noun “gospel” for the Greek “evangel” but retains the Greek root for the adjective “evangelical” and the abstract class-noun “evangelicalism.” There was a time when certain Protestants were called Gospellers, but the obvious link between “gospel” and “evangelical” has now been largely obscured. As an abstract noun naming things that cannot be heard, seen, or touched, “evangelicalism” seems always in need of more concrete definition.
Here history helps to clarify the meaning. In common use, “evangelicalism” deals with the doctrines, practices, and history of a class of Protestants that emerged distinctively in the early modern period, endured for three centuries, and spread to five continents. “Evangelical” identified the churches of the Protestant Reformation and their teaching, especially the Lutheran evangelische church, but the origins of modern evangelicalism, as understood in the English-speaking world, are found more in the popular spiritual awakening of the following centuries in the North Atlantic region. Seventeenth-century movements of devotion such as Pietism, Puritanism, and the Anglican “holy living” tradition fused to generate a general spiritual awakening …
Source: Christianity Today Most Read