cedilla vs diacritical mark

cedilla and diacritical mark both are nouns.

Word	Noun	Adjective	Verb	Adverb
cedilla	Yes	No	No	No
diacritical mark	Yes	No	No	No

As nouns, diacritical mark is a hypernym of cedilla; that is, diacritical mark is a word with a broader meaning than cedilla:

cedilla: a diacritical mark (,) placed below the letter c to indicate that it is pronounced as an s
diacritical mark: a mark added to a letter to indicate a special pronunciation

Other hypernyms of cedilla include diacritic.

cedilla (noun)	diacritical mark (noun)
a diacritical mark (,) placed below the letter c to indicate that it is pronounced as an s	a mark added to a letter to indicate a special pronunciation