Mark over some German vowels (6)
I believe the answer is:
umlaut
'mark over some german vowels' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for umlaut that I've seen before include "German accent" , "Mark indicating changed vowel value in German" , "Dots over vowel, as in Koln" , "Diacritical mark (two dots) placed over a vowel in German to indicate a change in sound" , "Mark put over a vowel in German to indicate a different quality" .)