The Khorchin (Mongolian Qor?in, Chinese K?'?rqìn) dialect is a variety of Mongolian spoken in the east of Inner Mongolia, namely in Hinggan League, in the north, north-east and east of Hinggan and in all but the south of the Tongliao region. There were 2.08 million Khorchin Mongols in China in 2000, so the Khorchin dialect may well have more than one million speakers, making it the largest dialect of Inner Mongolia.
Historical /t/ has become modern /?/, and in some varieties, /s/ is replaced by /t?/. Then, *u (<*?<*u) has regressively assimilated to /?/ before *p, e.g. *putaha (Written Mongolian buda?-a) > pata 'rice'. However, less systematic changes that pertain only to a number of words are far more notable, e.g. *tital 'capacity'> Khorchin /x?tl/. This last example also illustrates that Khorchin allows for the consonant nuclei /l/ and /n/ (cp. [?ln] 'many').
The large vowel system developed through the depalatalization of consonants that phonemicized formerly allomorphic vowels, hence /oe/ and /?/. On the other hand, *ö is absent, e.g. Proto-Mongolic *ke > Kalmyk //, Khalkha /o?k/ 'colour', but Khorchin /u?/, thus merging with /u/./y/ is absent in the native words of some varieties and /?/ is completely restricted to loanwords from Chinese, but as these make up a very substantial part of Khorchin vocabulary, it is not feasible to postulate a separate loanword phonology. This also resulted in a vowel harmony system that is rather different from Chakhar and Khalkha: /u/ may appear in non-initial syllables of words without regard for vowel harmony, as may /?/ (e.g. /?tu/ 'horses' and /unt/ 'expensive'; Khalkha would have /?t?/ 'horses' and /unt?e/). On the other hand, /u/ still determines a word as front-vocalic when appearing in the first syllable, which doesn't hold for /?/ and /i/. In some subdialects, /?/ and /oe/ which originated from palatalized /a/ and /?/, have changed vowel harmony class according to their acoustic properties and become front vowels in the system, and the same holds for their long counterparts. E.g. *mori-bar 'by horse' > Khorchin [moe:roer] vs. Jalaid subdialect [moe:r?r].
Khorchin uses the old comitative /-l?/ to delimit an action within a certain time. A similar function is fulfilled by the suffix /-?ri/ that is, however, restricted to environments in the past stratum. In contrast to other Mongolian varieties, in Khorchin Chinese verbs can be directly borrowed; other varieties have to borrow Chinese verbs as Mongolian nouns and then derive these to verbs. Compare the new loan /t?lu-/ 'to ask for money' < zh?ngluó () with the older loan /t:l-/ 'to borrow' < jiè (?) that is present in all Mongolian varieties and contains the derivational suffix /-l-/.