Proto-Mongolic can be clearly identified chronologically with the language spoken by the Mongols during Genghis Khan's early expansion in the 1200-1210s.

Certain archaic words and features in Written Mongolian go back past Proto-Mongolic to Late Pre-Proto-Mongolic (Janhunen 2006).

An exception would be the voice suffix like -caga- 'do together', which can be reconstructed from the modern languages but is not attested in Middle Mongol.

[5] For Tabghach, the language of the founders of the Northern Wei dynasty, for which the surviving evidence is very sparse, and Khitan, for which evidence exists that is written in the two Khitan scripts (large and small) which have as yet not been fully deciphered, a direct affiliation to Mongolic can now be taken to be most likely or even demonstrated.

Middle Mongol had two series of plosives, but there is disagreement as to which phonological dimension they lie on, whether aspiration[7] or voicing.

[9] One prominent, long-running disagreement concerns certain correspondences of word medial consonants among the four major scripts (UM, SM, AM, and Ph, which were discussed in the preceding section).

[11] /h/ (also called /x/) is sometimes assumed to derive from */pʰ/, which would also explain zero in SM, AM, Ph in some instances where UM indicates /p/; e.g. debel > Khalkha deel.

[12] The palatal affricates *č, *čʰ were fronted in Northern Modern Mongolian dialects such as Khalkha.

In some words, word-final *n was dropped with most case forms, but still appears with the ablative, dative and genitive.

Moreover, the sound changes involved in this alternative scenario are more likely from an articulatory point of view and early Middle Mongol loans into Korean.

[18] In the ensuing discourse, as noted earlier, the term "Middle Mongol" is employed broadly to encompass texts scripted in either Uighur Mongolian (UM), Chinese (SM), or Arabic (AM).

As this adjective functioned parallel to ügej 'not having', it has been suggested that a "privative case" ('without') has been introduced into Mongolian.

[32] The distinction between male, female and plural subjects exhibited by some finite verbal suffixes was lost.

[40] A few linguists have grouped Mongolic with Turkic, Tungusic and possibly Koreanic or Japonic as part of the controversial Altaic family.

Another problem lies in the sheer comparability of terminology, as Western linguists use language and dialect, while Mongolian linguists use the Grimmian trichotomy language (kele), dialect (nutuɣ-un ayalɣu) and Mundart (aman ayalɣu).