res·er·voir (rĕzər-vwär′, -vwôr′, -vôr′)
1. A natural or artificial pond or lake used for the storage and regulation of water.
2. A receptacle or chamber for storing a fluid.
3. An underground accumulation of petroleum or natural gas.
4. Anatomy See cisterna.
5. A large or extra supply; a reserve: a reservoir of goodwill.
6. Medicine An organism or population that directly or indirectly transmits a pathogen while being virtually immune to its effects.
[French réservoir, from réserver, to reserve, from Old French reserver; see RESERVE.]
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.