consists of several dialects spoken in Tripura. Ethnologue lists Usoi (Kau Brung), Riang (Kau Bru), and Khagrachari ("Trippera") as separate languages; Mukchak (Barbakpur), though not listed, is also distinct, and the language of many Tripuri clans has not been investigated. The greatest variety is within Khagrachari, though speakers of different Khagrachari varieties can "often" understand each other. Khagrachari literature is being produced in the Naitong and Dendak varieties. Phonology Kókborok has the phonology of a typical Sino-Tibetan language. Vowels Kokborok has six vowel (monophthong) phonemes: /i u e w o a/. Early scholars of Kokborok decided to use the letter w as a symbol for a vowel that does not exist in English. In some localities, it is pronounced closer to [ɨ], and in others, it is pronounced closer to o. In Kokborok spelling, u is used for the sound in the diphthongs (used initially, spelled as ua) and (used finally, spelled as uo). It is also used for the diphthong (spelled wi) after m and p Consonants Ch is used for , while kh, ph, chh and th are used for , , and respectively. N' is the pronunciation of the nasal sound, e.g., in' (yes). Ng is a digraph and is generally used in the last syllable of a word, e.g., aming (cat), holong (stone). Ua is often used initially, e.g., uak (pig), uah (bamboo), uatwi (rain). Uo is often used finally, e.g., thuo (sleeping), buo (beat). Diphthongs A diphthong is a group of two vowels. The wi diphthong is spoken as ui after sounds of the letters m and p. Two examples are chumui (cloud) and thampui (mosquito). The ui diphthong is a variation of the wi diphthong. Other less frequent diphthongs, such as oi and ai, are called closing diphthongs. A closing diphthong refers to a syllable that does not end in a consonant. Syllables Most words are formed by combining the root with an affix: kuchuk is formed from the root chuk (to be high), with the prefix, ku. phaidi (come) is formed from the root phai (to come), with the suffix di. There are no Kókborok words beginning with ng. At the end of a syllable, any vowel except w can be found, along with a limited number of consonants: p, k, m, n, ng, r and l. Y is found only in closing diphthongs like ai and wi. Clusters "Clusters" are a group