Beta — written as the uppercase and lowercase letters Β β — is the second character of the Greek alphabet. In earlier stages of the language (see Ancient Greek) it represented a voiced bilabial stop [b]; in the form of modern Greek it denotes a voiced labiodental fricative [v]. In the traditional system of Greek numerals, beta has the numeric value 2.
History and descendants
Over several centuries of phonetic change during the Hellenistic and Roman periods, the pronunciation associated with beta shifted from [b] toward [v]. The Greek letter was the ancestor of alphabetic signs in other scripts: it gave rise to the Latin letter B, and was an important source for letters in the Cyrillic writing system (in modern Cyrillic alphabets the related letters represent the sounds /v/ and /b/).
Use of the symbol "beta" in modern fields
- In finance, "beta" commonly denotes a coefficient measuring an asset's sensitivity to movements in a market index (the market beta in capital asset pricing models).
- In the physical sciences (science), the name appears in contexts such as beta decay and beta particles in nuclear physics.
- In mathematics, the capital letter B is used to name the Beta function (also called the Euler beta function) among other uses.
- In statistical notation, the lowercase beta symbol is widely used; for example, the probability of a type II error is commonly written as β in texts on statistics.