The article presents the influence of French on compound words in Breton language. One can observe that this influence is the strongest in the common compound words, particularly in these which relate to everyday and public life – it stems for the long domination of French and voluntary abandonment of the Breton language in favour of French by Bretons. However, thanks to present efforts to protect and restore this language, one can observe a formation of own Breton words for new phenomena and scientific discoveries, which in French and other languages are described with the use of Latin and Greek compound words. By comparing foreign influences in word formation of the Polish language, we can notice analogous situations in the case of the common composition (i.e. strong influences in everyday vocabulary, when the language is dominated by other languages). However, when it comes to Latin- Greek compositions, Polish readily uses and adopts such words, which have already become internationalisms, because, as a currently strong language, it is not afraid of losing its own identity.