God uses the word ‘sign’ in Isaiah 7:14, in the plan of Redemption. A sign is used by God as a means of communicating an important truth. Jesus in the New Testament speaks many times also about signs, as in St Matthew’s Gospel, speaking of the signs of the times. According to the Book of Wisdom, creation itself is a sign. The miracles by Jesus are signs: e.g. at Cana, the change of water into wine by the Lord manifested his glory.