Omega

Omega is the last letter of the Greek alphabet, and Alpha is the first, so “Alpha and Omega” works like saying from A to Z. Four times in Revelation the Lord uses it of himself. Chapter 1 adds “the beginning and the ending” and calls him the Almighty, and chapter 22 adds “the first and the last.” In 21:6 it comes with a promise: “I will give unto him that is athirst of the fountain of the water of life freely.” Revelation 21 is where to read it in full.

4 verses

Revelation

Revelation 1:8

I am Alpha and Omega, the beginning and the ending, saith the Lord, which is, and which was, and which is to come, the Almighty.

Revelation 1:11

Saying, I am Alpha and Omega, the first and the last: and, What thou seest, write in a book, and send it unto the seven churches which are in Asia; unto Ephesus, and unto Smyrna, and unto Pergamos, and unto Thyatira, and unto Sardis, and unto Philadelphia, and unto Laodicea.

Revelation 21:6

And he said unto me, It is done. I am Alpha and Omega, the beginning and the end. I will give unto him that is athirst of the fountain of the water of life freely.

Revelation 22:13

I am Alpha and Omega, the beginning and the end, the first and the last.

From Easton's Bible Dictionary

Matthew George Easton, 1897

(Rev. 1:8), the last letter in the Greek alphabet. (See A.)

From Smith's Bible Dictionary

William Smith, 1884

The last letter of the Greek alphabet. It is used metephorically to denote the end of anything (Revelation 1:8,11)