Beta (?), n. [Gr. bh^ta.] The second letter of the Greek alphabet, B, β. See B, and cf. etymology of Alphabet. Beta (B, β) is used variously for classifying, as: (a) (Astron.) To designate some bright star, usually the second brightest, of a constellation, as, β Aurigæ. (b) (Chem.) To distinguish one of two or more isomers; also, to indicate the position of substituting atoms or groups in certain compounds; as, β-naphthol. With acids, it commonly indicates that the substituent is in union with the carbon atom next to that to which the carboxyl group is attached.[Webster 1913 Suppl.]