Proto-Dené–Caucasian is the reconstructed hypothetical common ancestor of the Dené–Caucasian languages, a proposed language superfamily to which Basque, North Caucasian, Burushaski, Sino-Tibetan, Yeniseian, Na-Dené and possibly also other language families may belong. Dene-Caucasian is not supported by most historical linguists and is generally regarded as a fringe theory. Reconstructed phonology As with Proto-Indo-European and Proto-Uralic, linguists working on reconstructions of the Proto-Dené–Caucasian language usually do not use the IPA. To facilitate comparisons with the literature, Starostin's transcription (largely identical to Bengtson's) is used in this section, followed by the IPA equivalents between slashes (for phonemes) or brackets (for actual phones). It differs from the IPA especially in the affricates, each of which is written with a single character, and the laterals. This convention strongly resembles the APA. As in all reconstructions of proto-languages, every value in the tables below is a hypothesis and may change as more work is done. Consonants ¹ As in today's Caucasian languages, all plosives and affricates (except and ) were seemingly either voiced, ejective, or aspirated. Because aspiration alone was not phonemic, it is not shown in the phonemic transcription of Proto-Dené–Caucasian, Caucasian languages, or Na-Dené languages in this article. ² These sounds were probably not separate phonemes, but allophones of their voiceless counterparts. Vowels The reconstruction of vowels is rather tentative. Both long and short vowels are reconstructed, but it is as yet uncertain whether the distinction was phonemic or not. It was, however, crucial for phonological developments in the daughter languages. The Proto-Dené–Caucasian root Root structure The most basic root structure in Proto-Dené–Caucasian is reconstructed as follows: Nominal and verbal roots: */C1VC2V/ */C1VC2VC3V/ Verbal and adjectival roots may be preceded by class prefixes and have the following structure (/=/ denotes the position of a class marker): */=VC1V/ */=VC1VC2/ Pronominal roots may be monosyllabic: */CV/ Prosodical features The evidence from Sino-Tibetan, Yenisian and North Caucasian appears to support the existence of dynamic accent (marked with an acute above the vowel): Stress on the penultimate syllable: */C1V́C2V/ */C1VC2V́C3V/ Stress on the final syllable: */C1VC2V́/ */C1VC2VC3V́/ Regular correspondences Suprasegmental The stressed penultimate syllables in PDC give rise to the morpheme-wide tenseness in PNC. As only fricatives and affricates can be tense in PNC, their absence makes tense morphemes indistinguishable from the lax ones. The loss of the slot-3 glottal stop after long vowels in PY is another problem for the clear determination of stress in PDC.