al·pha / ˈalfə/ • n. 1. the first letter of the Greek alphabet (Α, α), transliterated as “a.” ∎  [as adj.] denoting the first of a series of items or categories, e.g., forms of a chemical compound: alpha interferon. ∎ short for alpha test. ∎  (Alpha) [followed by Latin genitive] the first (typically the brightest) star in a constellation: Alpha Centauri. ∎  [as adj.] relating to alpha decay or alpha particles: an alpha emitter. ∎  (of animals in a group) the socially dominant individual: he rose to be alpha male of his troop at the very early age of 16.2. a code word representing the letter A, used in radio communication.• symb. ∎  (α) a plane angle. ∎  (α) angular acceleration. ∎  (α) Astron. right ascension.

alpha the first letter of the Greek alphabet (A, α), transliterated as ‘a’. The phrase alpha and omega ‘the beginning and the end’ (omega is the last letter of the Greek alphabet, as alpha is the first) is especially used by Christians as a title for Jesus.