En ou ès

Question

Why it says "docteur ès sciences mathématiques" rather than "docteur en sciences mathématiques"? Does it have different meaning?

Accepted Answer

Hi Henryk, 
It is an old French contraction used for  'en les'  (from the Xth Century I believe) which is still used for qualifications.
Take a look at the following page I found to shade more light on the subject. But an interesting question which I am sure lots of students will have asked themselves.
https://www.larousse.fr/dictionnaires/francais/%C3%A8s/30910

Answer

Thanks Cécile,I found also this: https://www.dictionnaire-academie.fr/article/A9E2534