1. An abundance or excess of something: "[the pitcher's] sinker that clocks in the low nineties ... resulting in a plethora of weakly hit groundballs" (Buzz Bissinger).
2. An excess of blood in the circulatory system or in one organ or area.
[Late Latin plēthōra, from Greek, from plēthein, to be full; see pelə-1 in the Appendix of Indo-European roots.]
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.