n. pl. ex·ter·nal·i·ties
a. The condition or quality of being external or externalized.
b. Something that is external.
2. A cost or benefit that affects people other than those involved in the economic activity that produced it and that is not reflected in prices: pollution and other negative externalities.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 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.