Proto-Kra–Dai (typically abbreviated as PKD) is the proposed reconstructed ancestor of the Kra–Dai languages.

No full reconstruction of Proto-Kra–Dai has been published to date, although tentative reconstructions of many Proto-Kra–Dai roots have been attempted from time to time. Some preliminary Proto-Kra–Dai forms have been reconstructed by Benedict (1975)^[1] and Wu (2002). Wu (2002) presents a reconstruction of Proto-Kra–Dai phonemes, which is based on data from the Tai, Kam-Sui, Hlai, and Kra branches.^[2]

Liang & Zhang (1996) propose a reconstruction of Proto-Kra–Dai (Chinese: 原始侗台语) initials and finals, using data from all Kra–Dai branches except for Kra and Jiamao.^[3]

Proto-Kra–Dai has the finals *-l and *-c, which have been lost in most present-day Kra–Dai languages.^[4] It also has the final stops *-p, *-t, *-k and final nasals *-m, *-n, *-ŋ.^[4]

Ostapirat (2023) proposes the following consonant inventory for Proto-Kra–Dai, which is relatively simple compared to that of Proto-Tai and other lower-level reconstructions.^[5]

Norquest (2020) proposes the preglottalized sonorants *ʔb, *ʔd, *ʔɖ, *ʔɟ for Proto-Kra–Dai, as part of a four-way phonation distinction in Kra-Dai sonorants consisting of preaspirated, voiceless, plain, and preglottalized sonorants. Norquest (2020) also reconstructs velarized initial consonants (*Cˠ-) in Proto-Kra–Dai.^[6]

Below is a table of Proto-Kra–Dai pre-syllables and their developments as proposed by Norquest (2020).^[6]

Ostapirat (2023) considers many Proto-Tai spirants and rhotics to have developed from the intervocalic lenition of Proto-Kra–Dai medial obstruents. Voicing in the Proto-Tai initial is determined by the voicing of the preceding consonant in the Proto-Kra–Dai form.^[5]

Some Proto-Kra–Dai sesquisyllabic consonant onsets reconstructed by Ostapirat (2023) are:^[5]

Liang & Zhang (1996) propose the following reconstructions of Proto-Kra–Dai (Chinese: 原始侗台语) initials and finals, using data from all Kra–Dai branches except for Kra and Jiamao.^[3]

Initial consonants

• Plain stop initials
  • *p, *pw, *pl, *plw, *pr
  • *t, *tl, *tr
  • *k, *kw, *kl, *klw, *kr, *krw
  • *q, *ql, *qr, *ʔ
  • *b, *bw, *bl, *blw, *br
  • *d, *dl, *dr
  • *g, *gw, *gl, *glw, *gr, *grw, *ɢ
• Voiced aspirated initials
  • *bɦ, *bwɦ, *brɦ
  • *dɦ, *ndlɦ
  • *gɦ, *gwɦ
  • *ɣɦ, *ɣwɦ, *ɢɦ, *ʁɦ, *sɢrɦ
• Preglottalized initials
  • *ʔb, *ʔbw, *ʔbl, *ʔblw
  • *ʔd, *ʔdl, *ʔdr
  • *ʔm, *ʔml, *ʔmr
  • *ʔn, *ʔnl, *ʔnr, *ʔȵ, *ʔŋ, *ʔŋw
• Voiceless nasal initials
  • *m̥, *m̥w, *m̥l, *m̥r, *m̥rw
  • *n̥, *n̥l, *ȵ̥, *ȵ̥w, *ŋ̥, *ŋ̥w
• Plain nasal initials
  • *m, *mw, *ml, *mr
  • *n, *nr, *ȵ, *ŋ, *ŋw, *ŋr, *ɴl
• Prenasalized initials
  • *mp, *mpl, *mpr
  • *nt, *ntl, *ntr
  • *ŋk, *ŋkw, *ŋkl
  • *mb, *mbl, *mbr
  • *nd, *ndl, *ndr
  • *ŋg, *ŋgl, *ŋgr
• Glide and liquid initials
  • *ʔw, *ʔr, *ʔj
  • *w̥, *l̥, *r̥, *j̥
  • *w, *l, *r, *j
• Fricative initials
  • *s, *sw, *sl, *sr, *ɕ, *x, *xw, *xl, *xr, *h
  • *z, *zl, *zr, *ʑ, *ɣ, *ɣw, *ɣl, *ʁ, *ɦ
• Initial clusters beginning with fricatives
  • *xp, *xpl, *xpr, *xt, *xk, *xkw, *xkl, *xklw, *xkr, *xkrw, *xq, *xql
  • *sp, *spw, *spl, *st, *stl, *str, *sk, *skw, *skl, *skr, *skrw, *sq, *sqr
  • *zb, *zd, *zdw, *zgr

Vowels and diphthongs

• *a, *a, *i̯a, *u̯a, *ɯ̯a
• *ə̯, *i̯ə, *u̯ə
• *ɛ, *i̯ɛ, *e, *i̯e
• *ɔ, *u̯ɔ, *ɯ̯ɔ, *o, *i̯o, *u̯o, *ɯ̯o
• *i̯, *u̯i, *ie ,iə, *ia, *iɛ
• *u, *i̯u, *ɯ̯u, *ue, *uə, *ua, *uo, *uɔ, *uɯ
• *ɯ, *ɯe, *ɯə, *ɯa, *ɯɔ, *ɯu

Weera Ostapirat (2018a)^[7] reconstructs disyllabic forms for Proto-Kra–Dai, rather than sesquisyllabic or purely monosyllabic forms. His Proto-Kra–Dai reconstructions also contains the finals */-c/ and */-l/.^[8] Ostapirat (2018b:113)^[9] lists the following of his own Proto-Kra–Dai reconstructions.

Notes:

• */K-/: either /k-/ or /q-/
• */C-/: unspecified consonant
• */T-/ and */N-/ are distinct from */t-/ and */n-/.

Some additional tentative Proto-Kra–Dai reconstructions by Ostapirat (2023) include the following.^[5]

Norquest (2020) lists the following of his own Proto-Kra–Dai and other lower-level reconstructions.^[6]

Norquest (2021) provides the following lower-level reconstructions for each branch of Kra–Dai.^[10]

Note that like Jiamao, Proto-Be does not distinguish between tone categories B and C, but rather only has an X category, which Chen (2018) names as tone category BC.^[11]

• Austro-Tai languages
• Old Chinese
• Proto-Austronesian language
• Proto-Hmong–Mien language
• Proto-Austroasiatic language

• Sagart, Laurent. 2019. A model of the origin of Kra-Dai tones. Cahiers de Linguistique Asie Orientale, 48(1), 1–29. doi:10.1163/19606028-04801004
• Sagart, Laurent. 2020. "Labial fortitions in Kra-Dai." In Sino-Tibetan-Austronesian.
• Norquest, Peter (2021). "Classification of (Tai-)Kadai/Kra-Dai languages". The Languages and Linguistics of Mainland Southeast Asia. De Gruyter. pp. 225–246. doi:10.1515/9783110558142-013. ISBN 9783110558142. S2CID 238672319.