Sumerian phonology

Sumerian phonology is flawed and incomplete because of the lack of native speakers, the transmission through the filter of Akkadian phonology and the difficulties posed by the cuneiform script. There is relatively little consensus, even among reasonable Sumerologists, in comparison to the state of most modern or classical languages. Verbal morphology in particular is hotly disputed. In addition to the general grammars, there are many monographs and articles about particular areas of Sumerian grammar, without which a survey of the field could not be considered complete. As I.M. Diakonoff observes, "when we try to find out the morphophonological structure of the Sumerian language, we must constantly bear in mind that we are not dealing with a language directly but are reconstructing it from a very imperfect mnemonic writing system which had not been basically aimed at the rendering of morphophonemics".

Assumed phonological or morphological forms will be between slashes //, with plain text used for the standard Assyriological transcription of Sumerian. Most of the following examples are unattested.

Consonants
Sumerian is conjectured to have at least the following consonants:


 * a simple distribution of six stop consonants, in three places of articulation distinguished by aspiration, though later stages may have featured voicing:
 * p (voiceless aspirated bilabial plosive),
 * t (voiceless aspirated alveolar plosive),
 * k (voiceless aspirated velar plosive),
 * As a rule, /p/, /t/ and /k/ did not occur word-finally.
 * b (voiced unaspirated bilabial plosive),
 * d (voiced unaspirated alveolar plosive),
 * g (voiced unaspirated velar plosive).
 * a phoneme usually represented by /ř/ (sometimes written dr) that was probably a voiceless aspirated alveolar affricate. This phoneme later became /d/ or /r/ in northern and southern dialects, respectively.
 * a simple distribution of three nasal consonants in similar distribution to the stops:
 * m (bilabial nasal),
 * n (alveolar nasal),
 * g̃ (frequently printed ĝ due to typesetting constraints, increasingly transcribed as ŋ) (likely a velar nasal, as in sing, it has also been argued to be a labiovelar nasal or a nasalized labiovelar ).
 * a set of three sibilants:
 * s, likely a voiceless alveolar fricative,
 * z, likely a voiceless unaspirated alveolar affricate,, as shown by Akkadian loans from /s/=[t͡s] to Sumerian /z/. In early Sumerian, this would have been the unaspirated counterpart to /ř/.
 * š (generally described as a voiceless postalveolar fricative,, as in ship),
 * a velar fricative /ḫ/ (sometimes written h).
 * two liquid consonants:
 * l (a lateral consonant),
 * r (a rhotic consonant).

Hypothetical consonants
The existence of various other consonants has been hypothesized based on graphic alternations and loans, though none have found wide acceptance. For example, Diakonoff lists evidence for two l-sounds, two r-sounds, two h-sounds, and two g-sounds (excluding the velar nasal), and assumes a phonemic difference between consonants that are dropped word-finally (such as the g in zag > za3) and consonants that remain (such as the g in lag). Other "hidden" consonant phonemes that have been suggested include semivowels such as and, and a glottal fricative  or a glottal stop that could explain the absence of vowel contraction in some words —though objections have been raised against that as well. A recent descriptive grammar by Bram Jagersma includes /j/, /h/, and /ʔ/ as unwritten consonants, with the glottal stop even serving as the first-person pronominal prefix.

Very often, a word-final consonant was not expressed in writing – and was possibly omitted in pronunciation – so it surfaced only when followed by a vowel: for example the /k/ of the genitive case ending -ak does not appear in e2 lugal-la "the king's house", but it becomes obvious in e2 lugal-la-kam "(it) is the king's house" (compare liaison in French).