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.’
    • ‘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.’
    • ‘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.’

Origin

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

Pronunciation

monophthong

/ˈmɒnəpθɒŋ//ˈmɒnəfθɒŋ/