a. Any of the cylindrical, keratinized, often pigmented filaments characteristically growing from the epidermis of a mammal.
b. A growth of such filaments, as that forming the coat of an animal or covering the scalp of a human.
2. A filamentous projection or bristle similar to a hair, such as a seta of an arthropod or an epidermal process of a plant.
3. Fabric made from the hair of certain animals: a coat of alpaca hair.
a. A minute distance or narrow margin: won by a hair.
b. A precise or exact degree: calibrated to a hair.
[Middle English her, from Old English hǣr.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 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.