Diacritical mark placed over a letter to indicate a palatal nasal consonant, as in the Spanish señor (5)
I believe the answer is:
tilde
(Other definitions for tilde that I've seen before include "Squiggly mark" , "Mark over the letter 'n' in Spanish" , "Significant mark" , "Mark placed over N in Spanish" , "part of Sao Paulo, originally" .)