Alpha and Omega are the first and last letters of the Greek alphabet. When used symbolically in Christianity, they signify that God is "the beginning and the end," meaning that God is eternal.
Furthermore, the expression is commonly understood as a merism, which is a figure of speech that articulates the beginning of something and the ending of something, but the implication that it refers to all things in between as well.
As symbols, the Alpha and Omega were used in early Christianity and appeared in the Roman catacombs.
The Alpha and Omega symbols are often combined with the cross (#3 right), chi rho (#6 right), or other Christian symbols.
In Judaism
In Rabbinic literature, the word emet ("truth"), composed of the first and last letters of the Hebrew alphabet, is "the seal of God," and in Judaism it carries somewhat the same connotation as Alpha and Omega.
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