1. The first letter of the Greek alphabet. See Table at alphabet.
2. The first of a series; the beginning.
3. Astronomy The brightest star in a constellation.
a. 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 Ri = a + bRm, which measures the return on a security (Ri) for a given return on the market (Rm) where b is beta.
b. The return on an investment portfolio that can be attributed to the skill of the portfolio's manager rather than the performance of the market.
1. Being the highest ranked or most dominant individual of one's sex. Used of social animals: the alpha female of the wolf pack.
a. Being in the first position relative to a designated carbon atom in an organic molecule at which an atom or a group may be substituted.
b. Referring to the first of a group of isomers, or molecules of similar origin or properties, determined arbitrarily by those who discover or classify them. Used in combination: alpha-tocopherol.
[Greek, of Phoenician origin; see ʾlp in the Appendix of Semitic roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.
American Heritage Dictionary Products
The American Heritage Dictionary, 5th Edition
The American Heritage Dictionary of Idioms
The American Heritage Roget's Thesaurus
Curious George's Dictionary
The American Heritage Children's Dictionary
The American Heritage Dictionary of Indo-European Roots
The American Heritage Student Grammar Dictionary
The American Heritage Desk Dictionary + Thesaurus
The American Heritage Science Dictionary
The American Heritage Dictionary of Business Terms
The American Heritage Student Dictionary
The American Heritage Essential Student Thesaurus