n. pl. stim·u·li (-lī′)
1. Something causing or regarded as causing a response.
2. An agent, action, or condition that elicits or accelerates a physiological or psychological activity or response.
a. Something that incites or rouses to action; an incentive: "Works which were in themselves poor have often proved a stimulus to the imagination" (W.H. Auden).
b. Government spending designed to generate or increase economic activity.
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.