re·in·force also re-en·force or re·en·force (rē′ĭn-fôrs)
tr.v. re·in·forced, re·in·forc·ing, re·in·forc·es also re-en·forced or re-en·forc·ing or re-en·forc·es or re·en·forced or re·en·forc·ing or re·en·forc·es
1. To give more force or effectiveness to; strengthen: The news reinforced her hopes.
2. To strengthen (a military force) with additional personnel or equipment.
3. To strengthen by adding extra support or material.
4. To increase the number or amount of; augment.
a. To reward (an experimental subject, for example) with a reinforcer subsequent to a desired response or performance.
b. To encourage (a response) by means of a reinforcer.
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.