n. pl. en·er·gies
1. The capacity for work or vigorous activity: Who has the energy to climb that trail? See Synonyms at strength.
a. also energies Exertion of vigor or power: a project requiring a great deal of time and energy; devoted her energies to writing songs.
b. Vitality and intensity of expression: a speech delivered with energy and emotion.
c. Informal A nonphysical force or quality perceived as inhering in a particular place, person, or situation: was turned off by the group's negative energy.
a. Usable heat or power: Each year Americans consume a high percentage of the world's energy.
b. A source of usable power, such as petroleum or coal.
a. The capacity of a physical system to do work.
b. A form, amount, or level of this capacity: "a searing beam of 30 trillion protons, with energies up to 50 million electronvolts" (Science News).
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.