The word “theology,” from theos meaning God and logos meaning rational expression, means the rational interpretation of religious faith. Christian theology thus means the rational interpretation of the Christian faith.
At least three elements are included in that general concept of theology.
(1) Theology is intelligible. It can be comprehended by the human mind in an orderly, rational manner.
(2) Theology requires explanation. This, in turn, involves exegesis and systematization.
(3) The Christian faith finds its source in the Bible, so Christian theology will be a Bible-based study. Theology, then, is the discovery, systematizing, and presentation of the truths about God.

Ryrie, C. C. (1999). Basic Theology: A Popular Systematic Guide to Understanding Biblical Truth (pp. 12–13).