Alpha (uppercase Α, lowercase α; Αλφα) is the first letter of the Greek alphabet. In the system of Greek numerals it has a value of 1. It was derived from the Phoenician letter Aleph . Letters that arose from Alpha include the Latin A and the Cyrillic letter А.
Plutarch in Moralia, presents a discussion on why the letter alpha stands first in the alphabet. Ammonius asks Plutarch what he, being a Boeotian, thinks of Cadmus, the Phoenician who reputedly settled in Thebes and introduced the alphabet to Greece, placing alpha first because it is the Phoenician name for ox -- which, unlike Hesiod, the Phoenicians considered not the second or third, but the first of all necessities. "Nothing at all" Plutarch replied. He then added that he would rather be assisted by Lamprias, his own grandfather, than by Dionysus' grandfather, i.e. Cadmus. For Lamprias had said that the first articulate sound made is "alpha", because it is very plain and simple — the air coming off the mouth does not require any motion of the tongue — and therefore this is the first sound that children make.
The Homeric word "alphesiboios" (ἀλφεσίβοιος) is associated with both the root "alph-" and "ox". It is derived from "alphanō" (ἀλφάνω) meaning to yield, earn and "bous" (βοῦς) meaning ox, hence alphesiboios means bringing in or acquiring oxen.
According to Plutarch's natural order of attribution of the vowels to the planets, alpha was connected with the Moon. Oxen were also associated with the Moon in both early Sumerian and Egyptian religious symbolism, possibly due to the crescent shape of their horns.
Alpha, both as a symbol and term, is used to refer to or describe a variety of things, including the first or most significant occurrence of something. The New Testament has God declaring himself to be the "Alpha and Omega, the beginning and the end, the first and the last." (Revelation 22:13, KJV, and see also 1:8).
The uppercase letter alpha is not generally used as a symbol because it tends to be rendered identically to the uppercase latin A.