n. pl. im·pe·tus·es
1. An impelling force; an impulse.
2. The force or energy associated with a moving body.
a. Something that incites; a stimulus.
b. Increased activity in response to a stimulus: The approaching deadline gave impetus to the investigation.
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.