The Khalkha dialect (Mongolian script: ᠬᠠᠯᠬᠠ ᠠᠶᠠᠯᠭᠣ Qalq-a ayalγu, Mongolian Cyrillic: Халх аялгуу Khalkh ayalguu, [ˈxɑɮxɑ ˈæjɑɮ.xuː]) is a dialect of Mongolian widely spoken in Mongolia and according to some classifications includes such South Mongolian varieties such as Shiliin gol, Ulaanchab and Sönid. As it was the basis for the Cyrillic orthography of Mongolian, it is de facto the national language of Mongolia. The name of the dialect is related to the name of the Khalkha tribe and the Khalkha river.
There are certain differences between normative and spoken Khalkha. For example, the normative language uses proximal demonstratives based on the stem ʉː/n- (except for the nominative in [i̠n] and the accusative which takes the stem ʉːn-) and thus exhibits the same developmental tendency as exhibited by Oirat. On the other hand, the spoken languages also makes use of paradigms that are based on the stems inʉːn- and inĕn-. This seems to agree with the use in Chakhar Mongolian. The same holds for the distal demonstrative /tir/.
Khalkha may roughly be divided into Northern and Southern Khalkha which would include Sönid etc. Both varieties share affricate depalatalization, namely, /tʃ/ > /ts/ and /tʃʰ/ > /tsʰ/ except before *i, while Southern Khalkha patters with Chakhar and Ordos in that it exhibits a dissimilating deaspiration, e.g. *tʰatʰa > /tatʰ/. However, Mongolian scholars more often hold that the border between Khalkha and Chakhar is the border between the Mongolian state and the Chakhar area of South Mongolia.
Especially in the speech of younger speakers, /p/ (or /w/) > [ɸ] may take place, as in Written Mongolian qabtasu > Sünid [ɢaptʰǎs] ~ [ɢaɸtʰǎs] 'cover (of a book)'.
One of the classifications of Khalkha dialect in Mongolia divides it into 3 subdialects: Central, Western and Eastern. The orthography of the Mongolian Cyrillic alphabet is essentially based on the Central Khalkha dialect. Among the main differences is the pronunciation of initial letter х in feminine words which is in Central Khalkha is pronounced as it is written, pronounced as kh in Western Khalkha and as g in Eastern Khalkha. Example: хөтөл (Central Khalkha), көтөл (Western Khalkha), гөтөл (Eastern Khalkha). The initial letter х is pronounced in masculine words in Western Khalkha dialect as h (almost not heard) if the second consonant is voiceless, and is pronounced as gh in Eastern Khalkha. Example: хутга (Central Khalkha),) hутага (Western Khalkha), гутага (Eastern Khalkha). Initial т is pronounced in Eastern Khalkha dialect as d. Example: талх (Central Khalkha),) талк (Western Khalkha), далх (Eastern Khalkha).