1. Hostility that results in active resistance, opposition, or contentiousness. See Synonyms at enmity.
2. The condition of being an opposing principle, force, or factor: the inherent antagonism of capitalism and socialism.
3. Biochemistry Interference in the physiological action of a chemical substance by another having a similar structure.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 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.