I. noun 1. the second letter of the Greek alphabet ( Β, β), transliterated as ‘b’. 2. [as modifier] — denoting the second of a series of items, categories, forms of a chemical compound, etc. • beta carotene
• beta blocker.
(Brit.) a second-class mark given for a piece of work or an examination paper.
‹informal› short for beta test.
5. ( Beta) [followed by Latin genitive] —
[Astronomy] the second (typically second-brightest) star in a constellation
• Beta Virginis.
6. [as modifier] — relating to beta decay or beta particles • beta emitters.
7. (also beta coefficient) — a measure of the movement in price of a security relative to the stock market as a whole, used to indicate possible risk. • a fund with a beta of 0.58 is less volatile.
– origin via Latin from Greek.