1. The first letter of the Greek alphabet.
2. The first one; the beginning.
3. Chemistry. The first position from a designated carbon atom in an organic molecule at which an atom or radical may be substituted.
4. Astronomy. The brightest or main star in a constellation.
5. The mathematical estimate of the return on a security when the return on the market as a whole is zero. Alpha is derived from a in the formula R_i = a + bR_m, which measures the return on a security (R_i) for a given return on the market (R_m) where b is beta.

1. Being the highest ranked or most dominant individual of one's sex. Used of social animals: the alpha female of the wolf pack.
2. Chemistry. Closest to the functional group of atoms in an organic molecule.
3. Alphabetical.

[Greek, of Phoenician origin.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.