The first eighteen verses of the gospel form both a summary of what the gospel is about and an introduction to it. The word 'prologue' comes from two Greek words and means 'a passage which goes in front.' The style and vocabulary are distinctive and nowhere else in the gospel is Jesus given the title of 'The Word' but right through the gospel he is the Word of God in the world and to the world. The roots of the prologue are in the Old Testament. The style and rhythm of Hebrew poetry lies behind the Greek in which the prologue is written. Major themes of the gospel, such as life, light, darkness, truth, witness, glory, the world, are introduced; the thought of the prologue is very concentrated and can only be understood fully as the gospel proceeds.