son·o·rous (sŏnər-əs, sōnər-əs, sə-nôrəs)
1. Having or producing sound.
2. Having or producing a full, deep, or rich sound.
3. Impressive in style of speech: a sonorous oration.
4. (also sōnər-əs) Produced in the manner of a sonorant.
[From Latin sonōrus, from sonor, sound, from sonāre, to sound; see swen- in the Appendix of Indo-European roots.]
Usage Note: Traditionally, sonorous was stressed on the second syllable, but the pronunciation with stress on the first syllable is now much more common in American English, with either a short o (sŏnər-əs) or a long o (sōnər-əs). In our 2016 survey, a significant majority of the Usage Panel—64 percent—preferred (sŏnər-əs), while 26 percent preferred (sōnər-əs) and only 9 percent of the Usage Panel preferred the traditional (sə-nôrəs) pronunciation.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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