“The Chi Rho is one of the earliest cruciform symbols used by Christians. It is formed by superimposing the first two letters of the word “Christ” in Greek, chi = ch and rho = r . Although not technically a cross, the Chi Rho invokes the crucifixion of Jesus as well as symbolizing his status as the Christ. The earliest evidence of the Chi Rho symbol is Constantine’s use of it on the labarum, the imperial standard, in the early 4th century CE. Lactantius, a 4th century Christian apologist, reports that on the eve of the Battle of the Milvian Bridge in 312 CE, Constantine had a vision of God in which he was commanded to mark his men’s shields with the Chi Rho symbol. After Constantine’s success at the Milvian bridge, the Chi Rho became the official imperial insignia. Archaeologists have uncovered evidence demonstrating that the Chi Rho was emblazoned on the helmet and shield of Constantine as well as those of all of his soldiers. Coins and medallions minted during Constantine’s reign also bore the Chi Rho. By the year 350 CE, the Chi Rho began to be used on Christian sarcophagi and frescoes. [A.E.M.] “ (Definition taken from the University of Rochester)
The Greek symbols on the left and right are Alpha & Omega. The beginning and the end. In the Greek alphabet, in which the New Testament was written, alpha is the first letter and omega is the last. In the Book of Revelation, God says, “I am Alpha and Omega, the first and the last,” meaning that God remains from the beginning to the end of time.