A French letter might have one

• Mark placed under the letter c
• Mark in the intersection of 58-Across and 43-Down
• Janet's fiancГ© in "The Rocky Horror Picture Show"
• Mark suggesting a 'c' should be pronounced an 's'
• Spanish diacritic
• Janet's fiancé in "The Rocky Horror Picture Show"
• Mark under a French c
• Mark made under a 'c'

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
cedilla \ce*dil"la\ (s[-e]*d[i^]l"l[.a]), n. [Sp. cedilla, cf. F. c['e]dille; dim. of zeta, the Gr. name of the letter z, because this letter was formerly written after the c, to give it the sound of s.] A mark placed under the letter c [thus, [,c ...

Wikipedia Word definitions in Wikipedia
A cedilla ( ; from Spanish ), also known as cedilha (from Portuguese) or cédille (from French), is a hook or tail ( ¸ ) added under certain letters as a diacritical mark to modify their pronunciation. In Catalan , French , and Portuguese , it is used only ...