diacritical mark vs diacritic

diacritical mark and diacritic both are nouns.

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

As nouns, diacritical mark and diacritic are synonyms defined as:

diacritical mark and diacritic: a mark added to a letter to indicate a special pronunciation

diacritical mark (noun)	diacritic (noun)
a mark added to a letter to indicate a special pronunciation	a mark added to a letter to indicate a special pronunciation

diacritical mark (adjective)	diacritic (adjective)
	capable of distinguishing