Syllable structure is highly variable. The most common types of syllable are CVV and CVC. Consonant clusters are common at either the onset or coda, but rarely both if ever. Sonorants and fricatives can appear as the nucleus of a syllable.
| Bilabial | Dental | Alveolar | Palatal | Velar | Uvular | Pharyngeal | Glottal | ||
|---|---|---|---|---|---|---|---|---|---|
| Nasal | ʰm m | n | ŋ | ||||||
| Stop | p b | t d | k kʰ g | q ɢ | ʔ | ||||
| Fricative | f v | θ ð | s z | ʃ ʒ | x | ħ | |||
| Affricate | pɸ bβ | ||||||||
| Liquid | ɬ l | ||||||||
| Approximant | w | j |
| Front | Center | Back | |
|---|---|---|---|
| Close | i | u | |
| Mid | ə | ||
| Open | a | ɑ |
Proto-World has four phonemic tones, including three register tones and one contour tone: high (˥), mid/neutral (˧), low (˩), and 51-falling (˥˩). Typically this is marked orthographically with diacritics on the vowel. Alternatively, it can be marked by a number after the syllable: high (1), mid/neutral (0 or unmarked), low (2), falling (3).