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. |