§2. Classification of Sounds
The simple Vowels are a, e, i, o, u, y.
The Diphthongs are ae, au, ei, eu, oe, ui, and, in early Latin, ai, oi, ou. In the diphthongs both vowel sounds are heard, one following the other in the same syllable.
J. H. Allen and J. B. Greenough, New Latin Grammar (Boston: Ginn, 1903). Text provided under a CC BY-SA license by Perseus Digital Library, http://www.perseus.tufts.edu, with funding from the National Endowment for the Humanities.