[40]. Short vowels. a sounded approximately like the English a in the first syllable of aha; e, i, o, and u sounded like e in step, i in pit, o in obey, and u in pull respectively.
[41]. Latin short a did not differ, except in quantity, from long ā; it never had the ‘flat’ sound of English a in pat. In the case of the other vowels, i, e, o, and u, the long vowels were closer ([46]) than the short ones. This is the same difference which the English shows in keen (long and close) and kin (short and open); pool (long and close) and pull (short and open). For this reason, open i is sometimes represented by e in inscriptions: as, ANEMA for anima, soul; and vea was the rustic pronunciation for via, road (Varro, R. R. 1, 2, 14).
[42]. Y, which was a sound borrowed from the Greek ([17]), sounded like German ü. The sound, which is missing in English, is formed with the tongue in position for i (in kin) and the lips rounded as for oo (in moon).
[CLASSIFICATION OF VOWELS.]
[43]. Vowels are divided according to the position of the tongue. Latin i and e are called front vowels, because the front part of the tongue is elevated. This elevation is greater for i than for e. Latin o and u are called back vowels, because they require an elevation of the rear part of the tongue. This elevation is greater for u than for o. Latin a holds an intermediate position, no part of the tongue being raised, while the front part is depressed.
[44]. In the formation of i and e, the tongue approaches the hard palate; hence these two vowels are also called palatal vowels. Similarly, o and u are called velar or guttural vowels, because in their formation the tongue approaches the soft palate (vēlum palātī).
[45]. o and u require a rounding of the lips (labia); hence they are called labial vowels. The same is true for y.
[46]. Comparing the vowels in English keen and kin, it will be noted that the passage between the tongue and the hard palate is narrower in the former than in the latter case. The ee in keen is therefore said to be a narrow or close vowel, while the i in kin is wide or open. See [41].
[DIPHTHONGS.]
[47]. Two unlike ([43-46]) vowels pronounced under one stress and as one syllable form a Diphthong. All diphthongs are long.