Alpha (A) is the first letter of the Greek alphabet. Omega is the last letter.
These letters occur in the text of Rev. 1:8, 11; 21:6; 22:13, and are represented by “Alpha” and “Omega” respectively (omitted in the Revised King James Version, New International Version, and the New Revised Standard Version 1:11). They mean “the first and last.” (Compare Hebrews 12:2; Isaiah 41:4; 44:6; Rev. 1:11, 17; 2:8.)
In the symbols of the early Christian Church, these two letters are frequently combined with the cross or with Christ’s monogram to indicate his divinity.