Amdo is one of the four main spoken Tibetic languages, the other three being Central Tibetan, Khams Tibetan, and Ladakhi. These four related languages share a common written script but their spoken pronunciations, vocabularies and grammars are different. These differences may have emerged due to geographical isolation of the regions of Tibet. Unlike Khams and Standard Tibetan, Amdo language is not a tonal language. It retains many word-initial consonant clusters that have been lost in Central Tibetan.