社會語言學家研究的是社會變異性與語言變異性之間的關係，探討一個語言在一段時間內發生的變異，並且不斷地進行歷史變遷，意即語言在社會情境中的表現型態。而歷史語言學家則是著重於語言的長期變遷，探討古代語言在當代的子語，以重建昔日語言的特徵。語言隨著時間而逐漸演變，在演變的過程中會出現兩個面向，其一為語言的變異、傳播與分裂成為子語，如法語及西班牙語是拉丁語的子語；另一個面向是語言的流失，在過去五百年，世界的語言多樣性已減少了一半，且學者預測本世紀將有二分之一的語言會消失。布列塔尼語是法國地區語言與少數民族語言之一，亦是法國唯一來自凱爾特語系的地區語言，本文將針對布列塔尼語在經歷遷徙、戰爭與語言政策的過程後，探討該語言的發展現況與其所面臨的挑戰，期能作為我國發展語言政策之參考。

Sociolinguists study the relationship between social variability and linguistic variability. They explore the variation of a language which has constantly changes over a period of time, the expression of language in social context. Meanwhile, historical linguists deal with the long-term changes of language. They explore the ancient language in contemporary sub-language, to reconstruct the characteristics of the old language, and the language gradually evolves with time. Therefore, there would be two aspects in the process of evolution about it. One is the variation, transmission and splitting of language into sub-language. For instance, French and Spanish are sub-languages of Latin. The other aspect is the loss of language. In the past five hundred years, the world's linguistic diversity has reduced in half, and scholars predict that one-half of the languages will disappear in this century. Breton is one of the French regional and minority languages. It is also the only regional language from the Celtic language in France. This paper tries to approach the evolution of the migration, wars and language policy about Breton in the history and to understand it's current state of development and meanwhile the challenges it faces as a reference for the development of minority language in Taiwan.