the first letter of the Greek alphabet (A, α).
the vowel sound represented by this letter.
the first; beginning.
(initial capital letter) Astronomy. used to designate the brightest star in a constellation.
Chemistry. one of two or more isomeric compounds.
the first in a series of related items: frequently used in chemistry and physics.
Chiefly British. a mark or grade corresponding to an A.
Compare (def 8), (def 9).

(of an animal) having the highest rank in a dominance hierarchy:
the alpha female of an elephant pack.
being the most dominant, powerful, or assertive person in a particular group.

See also .
Put the files in alpha order.
Chemistry. pertaining or linked to the carbon atom closest to a particular group in an organic molecule.
Contemporary Examples

Recruiting agents from amidst our rivals is the “the alpha and Beta of espionage,” says Weiner.
The CIA Tried Hard to Recruit Spies Among the Al Qaeda Prisoners at Gitmo Daniel Klaidman November 27, 2013

Paulson has run the alpha firm of the financial world, Goldman Sachs.
Even the Smart Guys Don’t Understand the Meltdown David Rothkopf October 6, 2008

But their tests were for gamma, not alpha, radiation, so they naturally would have missed any polonium diagnosis.
Bringing Up Yasir Arafat’s Body Tracy McNicoll November 23, 2012

alpha Centauri sought to write the next part of that story: the game aspired to tell “a history of the future.”
Nerdiness from Noah: Alpha Centauri Noah Kristula-Green March 28, 2013

And from the start, with top-notch production values certainly upgraded from a “YouTube video,” alpha House did.
Inside the Political Fun House: How ‘Alpha House’ Became Amazon’s First Big Hit Kevin Fallon October 23, 2014

Historical Examples

These have been named the alpha, beta, and gamma rays, respectively.
A Brief Account of Radio-activity Francis Preston Venable

This is but the alpha of decency, the first step of progress.
Another Sheaf John Galsworthy

The brightest star in the constellation is alpha, or Algenib, in the center of the row.
Astronomy with an Opera-glass Garrett Putman Serviss

The beginning is alpha and omega: the beginning and the end.
Appreciations and Criticisms of the Works of Charles Dickens G. K. Chesterton

This is a star of the first magnitude, alpha in the constellation of the Centaur.
The Astronomy of the Bible E. Walter Maunder

the first letter in the Greek alphabet (Α, α), a vowel transliterated as a
(Brit) the highest grade or mark, as in an examination

involving or relating to helium-4 nuclei: an alpha particle
relating to one of two or more allotropes or crystal structures of a solid: alpha iron
relating to one of two or more isomeric forms of a chemical compound, esp one in which a group is attached to the carbon atom to which the principal group is attached

(modifier) denoting the dominant person or animal in a group: the alpha male
(foll by the genitive case of a specified constellation) usually the brightest star in a constellation: Alpha Centauri
(communications) a code word for the letter a

c.1300, from Latin alpha, from Greek alpha, from Hebrew or Phoenician aleph (see aleph). The Greeks added -a because Greek words cannot end in most consonants. Sense of “beginning of anything” is from late 14c., often paired with omega (last letter in the Greek alphabet) as “the end.” Sense of “first in a sequence” is from 1620s. Alpha male was in use by c.1960 among scientists studying animals; applied to humans in society from c.1992.

alpha al·pha (āl’fə)

Symbol α The first letter of the Greek alphabet.

The first one in a series; the beginning.

The first position from a designated carbon atom in an organic molecule at which an atom or radical group may be substituted.


Characterizing the atom or radical group that is closest to the functional group of atoms in an organic molecule.

Relating to one of two or more closely related substances, as in stereoisomers.

Relating to or characterizing a polypeptide chain that is one of five types of heavy chains present in immunoglobins.

(Or “Input”) An extension of ALGOL 60 for the M-20 computer developed by A.P. Ershov at Novosibirsk in 1961. ALPHA includes matrix operations, slices, and complex arithmetic.
[“The Alpha Automatic Programming System”, A.P. Ershov ed., A-P 1971].

1. A compiler generator written by Andreas Koschinsky and described in his thesis at the Technische Universitaet Berlin. Alpha takes an attribute grammar and uses Bison and Flex to generate a parser, a scanner and an ASE evaluator (Jazayeri and Walter).
The documentation is in german.
2. DEC Alpha.


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    of or relating to an alpha receptor.

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  • Alpha and omega

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