M.Oppei t, in 1858, gave 318 forms as those "most in use." Of course it is at once evident that this alphabet cannot represent elementary sounds.

The Assyrian characters do, in fact, correspond, not to letters, according to our notion of letters, but to syllables.

These syllables are either mere vowel sounds, such as we represent by our vowels and diphthongs, or such sounds accompanied by one or two consonants.
The vowels are not very numerous.

The Assyrians recognize three only as fundamental--_a, i_, and _u_.

Besides these they have the diphthongs _ai_, nearly equivalent to _e_, and _au_, nearly equivalent to _o_.