Alpha (Greek ), (uppercase Α, lowercase α) 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 .

In both Classical Greek and Modern Greek, alpha represents the Open front unrounded vowel, .

Plutarch in ''Moralia'',Symposiacs, Book IX, questions II & IIIOn-line text at Adelaide library 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 HesiodIn his ''Works and Days'' Hesiod advised the early Greek farmers, "''First of all, get a house, then a woman and third, an ox for the plough''"
Hesiod, Works and Days at the Perseus Project., 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"''Iliad, XVIII, 593, (''''Entry at Liddell & Scott) is associated with both the root "alph-" and "ox". It is derived from "alphanō" (Entry at Liddell & Scott) meaning ''to yield, earn'' and "bous" () 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 Jesus 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.