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[al-fuh] /ˈæl fə/
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 beta (def 8), gamma (def 9).
  1. (of an animal) having the highest rank in a dominance hierarchy:
    the alpha female of an elephant pack.
  2. being the most dominant, powerful, or assertive person in a particular group.
See also alpha male.
Put the files in alpha order.
Chemistry. pertaining or linked to the carbon atom closest to a particular group in an organic molecule.
Origin of alpha
< Latin < Greek álpha < Semitic; cf. aleph Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for alpha
Contemporary Examples
Historical Examples
  • These have been named the alpha, beta, and gamma rays, respectively.

    A Brief Account of Radio-activity Francis Preston Venable
  • I am alpha and Omega, the beginning and the end, the first and the last.

    "Unto Caesar" Baroness Emmuska Orczy
  • The brightest star in the constellation is alpha, or Algenib, in the center of the row.

    Astronomy with an Opera-glass Garrett Putman Serviss
  • Took his finger off the button and there we were: alpha Centauri.

    Accidental Death Peter Baily
  • This is a star of the first magnitude, alpha in the constellation of the Centaur.

    The Astronomy of the Bible E. Walter Maunder
British Dictionary definitions for alpha


the first letter in the Greek alphabet (Α, α), a vowel transliterated as a
(Brit) the highest grade or mark, as in an examination
  1. involving or relating to helium-4 nuclei: an alpha particle
  2. relating to one of two or more allotropes or crystal structures of a solid: alpha iron
  3. 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
Word Origin
via Latin from Greek, of Phoenician origin; related to Hebrew āleph, literally: ox


(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
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for alpha

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.

Online Etymology Dictionary, © 2010 Douglas Harper
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alpha in Medicine

alpha al·pha (āl'fə)

  1. Symbol α The first letter of the Greek alphabet.

  2. The first one in a series; the beginning.

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

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

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

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

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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