Definition of "monophthong" []

• A single vowel articulated without change in quality throughout the course of a syllable, as the vowel of English bed. (noun)
• Two written vowels representing a single sound, as oa in boat. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "A monophthong, on the other hand, is a vowel sound that has the same sound throughout, like the/æ/sound in American English hat."
• "Putting the emphasis on the final syllable of Sotomayor is unnatural in English (which is why the president stopped doing it after the first time at his press conference), unlike my correspondent's simple preference for a monophthong over a diphthong, and insisting on an unnatural pronunciation is something we shouldn't be giving in to."
• "She's getting the Oklahoma monophthong -- mah, she says, for my, and raht, for right."