It is soft and harmonious, being highly vocalic in structure.
Every syllable is open, ending in a vowel sound, and short sentences may be constructed wholly of vocalic sounds.
Sumerian has a system of vowel harmony strikingly like that seen in all modern agglutinative languages, and it has also vocalic dissimilation similar to that found in modern Finnish and Esthonian.
Vocalic harmony is the internal bringing together of vowels of the same class for the sake of greater euphony, while vocalic dissimilation is the deliberate insertion of another class of vowels, in order to prevent the disagreeable monotony arising from too prolonged a vowel harmony.
The only consonants are k,1, m, n and p, which with the gently aspirated h, the five vowels, and the vocalic w, make up all the letters in use.