"Monpa" is a name for a group of communities, not for a single language, and the languages inside it are not all closely related. Dakpa in the Tawang basin and Tshangla through the middle valleys are both Tibeto-Burman but belong to different branches; Sherdukpen, Sartang and Lish on the foothill shelf belong to the Kho-Bwa group, whose position within Tibeto-Burman is still argued over; Brokpa, spoken by the yak herders, is Tibetic. None of them is a dialect of the others, and speakers of one do not automatically understand another. What unifies the belt linguistically is what is written rather than what is spoken: classical Tibetan is the liturgical and scholarly language across all of it, and until recently was the only written language most households encountered.
TshanglaTibeto-Burman
The most widely used Monpa language, spoken through Dirang, Kalaktang and the middle valleys. It is the same language as eastern Bhutan's Tshangla, with dialect differences no greater than those within either side.
बोलने वाले: Widely spoken here and the majority language of eastern Bhutan
DakpaTibeto-Burman, East Bodish
The speech of the Tawang basin, related to the Dzala and Dakpa varieties across the passes. Distinct enough from Tshangla that the two are not mutually intelligible.
BrokpaTibeto-Burman, Tibetic
Spoken by the high-pasture yak-herding households at Mago, Thingbu and Luguthang, and closer to Tibetan proper than the valley languages are.
SherdukpenTibeto-Burman, Kho-Bwa group
Spoken at Rupa and Shergaon on the foothill shelf. A separate community with its own festival calendar and its own history of seasonal movement down to the Assam plain.
Sartang and LishTibeto-Burman, Kho-Bwa group
Small language communities in the West Kameng foothills, closely related to Sherdukpen and among the least documented languages in the eastern Himalaya.
Classical Tibetan (Chöke)Tibeto-Burman, Bodish
The liturgical and literary language. Scripture, ritual, monastic education and the belt's manuscript tradition are all in it, and it is read rather than spoken.