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 ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.