Most people think of French as a nasal language, primarily because French has  nasal vowels. I used to think that nasal vowels did not pose a problem for  English students of French, but the more I engage with students in private  lessons, the more I realize that these vowels need more attention. 

Those of us who learned French “in the old days”, were taught that there are 4  nasal vowels: [ɑ̃] (as in “France”); [ɔ]̃ (as in “mon”); [ɛ]̃ (as in vingt); and [œ̃] (as  in “un” or “brun”). That last nasal vowel has been eliminated over the years, and the sound for that spelling is now the same as the vowel in “vingt”. Most  students of French will have no regrets about this change, since the sound for  that vowel was pretty unattractive and a bit hard to produce.