Because of the centrality of the πιστ- word group for the NT, it is used widely and regularly throughout the NT, but it does exhibit a semantic domain similar in in scope to that of אמן in the OT. πιστεύω can mean “give credence to a message and/or its bearer.” This meaning can be used in a non-religious sense, but the religious context clearly dominates. For example, God is frequently the object, important to note in contradistinction simply to a message or messenger. πίστις can mean “that which elicits trust, faith” which in certain contexts would mean “faithfulness, dependability” and “trust which one puts into practice, faith.” Because of this range of meanings, this word group has a strong connection to several important OT concepts, including belief, obedience, trust, hope, and faithfulness. Even so, the word group developed some specific meanings within the Christian context of the NT, including the content of that which is believed, the total attitude of life which could wax and wane with the human condition, and a specific orientation towards the act of God in Christ.
In all these areas faith is the act in virtue of which a man, responding to God’s eschatological deed in Christ, comes out of the world and makes a radical reorientation to God. It is the act in which the new eschatological existence of Christians is established, the attitude which is proper to this existence. As this attitude which constitutes existence, πίστις governs the whole of life.