Easton's Bible Dictionary: M. G. Easton, M.A., D.D.
Alpha, the first letter of the Greek alphabet, as Omega is the last. 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 R.V., 1:11). They mean "the first and last." (Comp. Heb. 12:2; Isa. 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 denote his divinity.