n. pl. ve·loc·i·ties
1. Rapidity or speed of motion; swiftness.
2. Physics A vector quantity whose magnitude is a body's speed and whose direction is the body's direction of motion.
a. The rate at which something acts or occurs: the velocity of metabolism of glucose in muscle cells.
b. The rate at which money changes hands in an economy.
[Middle English velocite, from Old French, from Latin vēlōcitās, from vēlōx, vēlōc-, fast; see weg- 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.