1. The minimal number of officers and members of a committee or organization, usually a majority, who must be present for valid transaction of business.
2. A select group.
3. The minimal density of bacterial cells that results in altered gene expression in a population of bacteria.
[Middle English, quorum of justices of the peace, from Latin quōrum, of whom (from the wording of a commission naming certain persons as members of a body), genitive pl. of quī, who; see kwo- 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.