Definition of: beta

(bā′tə, bē′-) noun
1. The second letter of the Greek alphabet (Β, β ): corresponding to English b. As a numeral it denotes 2.
2. The second object in any order of arrangement or classification, as, in astronomy the second brightest star in a constellation, in chemistry the second of a group of isomeric compounds, in botany the second subspecies, etc. [<Gk.]