a. Intensification and prolongation of sound, especially of a musical tone, produced by sympathetic vibration.
b. Intensification of vocal tones during articulation, as by the air cavities of the mouth and nasal passages.
c. Medicine The sound produced by diagnostic percussion of the normal chest.
2. Richness or significance, especially in evoking an association or strong emotion: "Israel, gateway to Mecca, is of course a land of religious resonance and geopolitical significance" (James Wolcott).
3. Physics The increase in amplitude of oscillation of an electric or mechanical system exposed to a periodic force whose frequency is equal or very close to the natural undamped frequency of the system.
4. Physics A subatomic particle having too short a lifetime to be observed directly and whose existence is inferred from a peak in the energy distribution of its decay products.
5. Chemistry The property of a compound having simultaneously the characteristics of two or more structural forms that differ only in the distribution of electrons. Such compounds are highly stable and cannot be properly represented by a single structural formula.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. 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.