ad·ven·ti·tious (ăd′vĕn-tĭshəs, -vən-)
1. Arising from an external cause or factor; not inherent: symmetry that was purely adventitious; adventitious circumstances that contributed to the plan's success.
a. Of or belonging to a structure that develops in an unusual place: adventitious roots.
b. Originating from an external source, especially as a contaminant: adventitious viruses in a cell culture.
c. Not congenital: adventitious deafness.
[From Latin adventīcius, foreign, from adventus, arrival; see ADVENT.]
(click for a larger image)adventitious
adventitious roots of a corn plant
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.