Phonology
Middle Mongol had the consonant phonemes /p, m, tʰ, t, s, n, l, r, t͡ʃʰ, t͡ʃ, j, kʰ, k, h/ and the vowel phonemes /i, e, y, ø, a, u, o/. The main difference to older approaches is that <γ> is identified with /h/ and /ɡ/ (sometimes as before /u/ and /y/), so that *pʰ for Proto-Mongolic cannot be reconstructed from internal evidence that used to be based solely on word-initial /h/ and the then rather incomplete data from Monguor.
Read more about this topic: Middle Mongolian Language