cedilla

n. mark placed under a consonant indicating pronunciation (i.e. "c" is pronounced "s")

A cedilla is a hook (¸) added under certain consonant letters as a diacritical mark to modify their pronunciation. The tail originated as the bottom half of a miniature cursive "z". The word "cedilla" is the diminutive of the old Spanish name for this letter, ceda, where it was first used. Modern Spanish, however, no longer uses this diacritic. An obsolete spelling of cedilla is cerilla.
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Noun
1. a diacritical mark (,) placed below the letter c to indicate that it is pronounced as an s
(hypernym) diacritical mark, diacritic

n. cedilla, mark placed under a consonant indicating pronunciation (i.e. "c" is pronounced "s")

(n.)
A mark placed under the letter c [thus, c], to show that it is to be sounded like s, as in facade.