1. Lying with the front or face downward.
2. Having a tendency; inclined. Often used in combination: paper that is prone to yellowing; an accident-prone child.
In a prone manner: The patient was lying prone on the bed.
[Middle English, inclined, disposed, from Latin prōnus, leaning forward; see per1 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.