Definition of monophthong in English:

monophthong

noun

Phonetics
  • A vowel that has a single perceived auditory quality.

    Contrasted with diphthong, triphthong
    • ‘A study of Tunisian women in Morocco showed that older women categorically use diphthongs/aw/and/aj /, while middle-aged women alternate between diphthongs and monophthongs.’
    • ‘One of the most notable features evident here is the vocalist's tendency to produce monophthongs in words like ‘I’ and ‘my’ so they sound more like ahh and mahh.’
    • ‘The monophthongs and diphthongs total 14 vowel sounds, perhaps the smallest vowel system of any long-established variety of English.’
    • ‘Urban Texas is also abandoning the ‘y’ sound after ‘n’, ‘d' and ‘t’, exchanging diphthongs for monophthongs.’

Origin

Early 17th century: from Greek monophthongos, from monos single + phthongos sound.

Pronunciation:

monophthong

/məˈnäpˌTHôNG//ˈmänə(f)ˌTHôNG/