[al.pha] n [ME, fr. L, fr. Gk, of Sem origin; akin to Heb aleph aleph] (13c) 1: the 1st letter of the Greek alphabet
2: something that is first: beginning
3: alpha wave
4: alpha particle
alpha adj (1863) 1: closest in the structure of an organic molecule to a particular group or atom "alpha-substitution"
2: socially dominant esp. in a group of animals