“In historical linguistics, vowel breaking, vowel fracture, or diphthongization is the change of a monophthong into a diphthong or triphthong.”

“Vowel breaking or diphthongization is a vowel shift in which a monophthong becomes a diphthong.”

“Monophthongization or smoothing is a vowel shift in which a diphthong becomes a monophthong.”

“There is evidence in French and Spanish that the monophthongization of au occurred independently in those languages.”

“In some languages, due to monophthongization, graphemes that originally represented diphthongs now represent monophthongs.”

“Many diphthongs had begun their monophthongization very early.”

“The monophthongs and diphthongs total 14 vowel sounds, perhaps the smallest vowel system of any long-established variety of English.”

“Younger women use the monophthongs characteristic of male speech.”

“The language has both monophthongs and diphthongs, and consonants can be voiced or unvoiced.”