Greek

In Ancient Greek, alpha was pronounced [a] and could be either phonemically long ([aː]) or short ([a]). Where there is ambiguity, long and short alpha are sometimes written with a macron and breve today: Ᾱᾱ, Ᾰᾰ.

• ὥρα = ὥρᾱ hōrā Greek pronunciation: [[hɔ́ːraː]](https://en.wikipedia.org/wiki/Help:IPA/Greek "Help:IPA/Greek") "a time"
• γλῶσσα = γλῶσσᾰ glôssa Greek pronunciation: [[ɡlɔ̂ːssa]](https://en.wikipedia.org/wiki/Help:IPA/Greek "Help:IPA/Greek") "tongue".
  
  In Modern Greek, vowel length has been lost, and all instances of alpha simply represent IPA: [[a]](https://en.wikipedia.org/wiki/Help:IPA/Greek "Help:IPA/Greek").
  
  In the polytonic orthography of Greek, alpha, like other vowel letters, can occur with several diacritic marks: any of three accent symbols (ά, ὰ, ᾶ), and either of two breathing marks (ἁ, ἀ), as well as combinations of these. It can also combine with the iota subscript (ᾳ).
  
  

Greek grammar

In the Attic–Ionic dialect of Ancient Greek, long alpha [aː] fronted to [ɛː]([[eta](https://en.wikipedia.org/wiki/Eta](<eta "Eta")). In Ionic, the shift took place in all positions. In Attic, the shift did not take place after epsilon, iota, and rho (ε, ι, ρ; e, i, r). In Doric and Aeolic, long alpha is preserved in all positions.[[3]](https://en.wikipedia.org/wiki/Alpha#cite_note-3)

• Doric, Aeolic, Attic χώρᾱ chṓrā — Ionic χώρη chṓrē, "country"
• Doric, Aeolic φᾱ́μᾱ phā́mā — Attic, Ionic φήμη phḗmē, "report"
  
  

Privative a is the Ancient Greek prefix ἀ- or ἀν- a-, an-, added to words to negate them. It originates from the Proto-Indo-European *n̥- (syllabic nasal) and is cognate with English un-.

Copulative a is the Greek prefix ἁ- or ἀ- ha-, a-. It comes from Proto-Indo-European *sm̥.

Mathematics and science

Main article: Alpha (disambiguation).

The letter alpha represents various concepts in physics and chemistry, including alpha radiation, angular acceleration, alpha particles, alpha carbon and strength of electromagnetic interaction (as Fine-structure constant). Alpha also stands for thermal expansion coefficient of a compound in physical chemistry. It is also commonly used in mathematics in algebraic solutions representing quantities such as angles. Furthermore, in mathematics, the letter alpha is used to denote the area underneath a normal curve in statistics to denote significance level[[4]](https://en.wikipedia.org/wiki/Alpha#citenote-4) when proving null and alternative hypotheses. In ethology, it is used to name the [dominant individual](https://en.wikipedia.org/wiki/Alpha(ethology) "Alpha (ethology)") in a group of animals. In aerodynamics, the letter is used as a symbol for the angle of attack of an aircraft and the word "alpha" is used as a synonym for this property. In mathematical logic, α is sometimes used as a placeholder for ordinal numbers.

The proportionality operator "∝" (in Unicode: U+221D) is sometimes mistaken for alpha.

The uppercase letter alpha is not generally used as a symbol because it tends to be rendered identically to the uppercase Latin A.

International Phonetic Alphabet

In the International Phonetic Alphabet, the letter ɑ, which looks similar to the lower-case alpha, represents the open back unrounded vowel.