Derived from the Latin doctrina, the concept refers to the body of teachings of a church or religion. In the Christian context, doctrine is what a church believes, teaches, and confesses, based on the word of God, giving the church an opportunity to define itself and its structure. What is believed is doctrine present in devotion, spirituality, and worship, whereas the church teaches worship based on the word of God and communicated to practitioners by proclamation, instruction, and theology. What is confessed refers to the testimony of the church against false teaching from within the church and attacks from outside of it, using polemics, apologetics, creeds, and dogma. In short, Christian doctrine is the saving knowledge derived from the word of God. The definition of the nature of the Trinity, virgin birth, transubstantiation, Immaculate Conception, Calvinist predestination, and grace are all examples of Christian doctrine, whereas the doctrine of the Buddha is summarized by the Four Noble Truths that define the root problem of human existence and the means of overcoming it.