for·mi·da·ble (fôrmĭ-də-bəl, fôr-mĭdə-)
1. Arousing fear, dread, or alarm: the formidable prospect of major surgery.
2. Inspiring awe, admiration, or wonder: "A woman of formidable intelligence and tenacity, [she] prides herself on being independent-minded" (Nan Levinson).
3. Difficult to undertake, surmount, or defeat: a formidable challenge; a formidable opponent.
[Middle English, from Old French, from Latin formīdābilis, from formīdāre, to fear, from formīdō, fear.]
for′mi·da·bili·ty, formi·da·ble·ness n.
Usage Note: Traditionally formidable has been pronounced with stress on the first syllable, but recently the pronunciation with stress on the second syllable, which is a common variant in British English, has seen increasing use in American English. However, the traditional pronunciation is still preferred by a large majority of the Usage Panel. In our 2008 survey, 73 percent favored the pronunciation with stress on the first syllable, and 27 percent favored the other pronunciation. Both pronunciations are acceptable, however.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 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.