This book aims at questioning the relationship between language and identity through the description of the sociolinguistic environment of the Dongxiang language, an under-studied Mongolic language spoken by the Dongxiang people in Southern Gansu, China. We will try to understand how, through interaction between the Dongxiang people and their neighbouring Hui communities, and their relationship to Standard Chinese, contacts have deeply modified the structure of the Dongxiang language. The Dongxiang linguistic community is in a state of unconscious diglossia: there is a de facto hierarchy of languages, but it is not recognised by speakers and is not expressed in the form of a general feeling of linguistic insecurity within the community. This is reflected in the Dongxiang language, where a specific morphology has been developed to integrate lexical and syntactic borrowings, making code-switching and code-mixing virtually impossible.