The limitations of the syllabic script in helping to determine the nature of Hittite phonology have been more or less overcome by means of comparative etymology and an examination of Hittite spelling conventions. Accordingly, scholars have surmised that Hittite possessed the following phonemes:
Vowels • Long vowels appear as alternates to their corresponding short vowels when they are so conditioned by the accent. • Phonemically distinct long vowels occur infrequently.
Consonants Plosives Hittite had two series of consonants, one which was written always
geminate in the original script, and another that was always simple. In
cuneiform, all consonant sounds except for glides could be geminate. It has long been noticed that the geminate series of plosives is the one descending from
Proto-Indo-European voiceless stops, and the simple plosives come from both voiced and voiced aspirate stops, which is often referred as
Sturtevant's law. Because of the typological implications of Sturtevant's law, the distinction between the two series is commonly regarded as one of voice. However, there is no agreement over the subject among scholars since some view the series as if they were differenced by
length, which a literal interpretation of the cuneiform orthography would suggest. Supporters of a length distinction usually point to the fact that
Akkadian, the language from which the Hittites borrowed the cuneiform script, had voicing, but Hittite scribes used voiced and voiceless signs interchangeably.
Alwin Kloekhorst also argues that the absence of assimilatory voicing is also evidence for a
length distinction. He points out that the word "
e-ku-ud-du – [ɛ́kʷːtu]" does not show any voice assimilation. However, if the distinction were one of voice, agreement between the stops should be expected since the
velar and the
alveolar plosives are known to be adjacent since that word's "u" represents not a vowel but
labialization.
Laryngeals Hittite preserves some very archaic features lost in other Indo-European languages. For example, Hittite has retained two of the three
laryngeals ( and word-initially). Those sounds, whose existence had been hypothesized in 1879 by
Ferdinand de Saussure, on the basis of vowel quality in other Indo-European languages, were not preserved as separate sounds in any attested Indo-European language until the discovery of Hittite. In Hittite, the phoneme is written as
ḫ. In that respect, Hittite is unlike any other attested Indo-European language and so the discovery of laryngeals in Hittite was a remarkable confirmation of Saussure's hypothesis. Both the preservation of the laryngeals and the lack of evidence that Hittite shared certain
grammatical features in the other early Indo-European languages have led some philologists to believe that the Anatolian languages split from the rest of Proto-Indo-European much earlier than the other divisions of the
proto-language. See #Classification above for more details. ==Morphology==