diacritic vs hacek

diacritic and hacek both are nouns.

Word	Noun	Adjective	Verb	Adverb
diacritic	Yes	Yes	No	No
hacek	Yes	No	No	No

As nouns, hacek is a hyponym of diacritic; that is, hacek is a word with a more specific, narrower meaning than diacritic:

diacritic: a mark added to a letter to indicate a special pronunciation
hacek: a diacritical mark (an inverted circumflex) placed above certain letters (such as the letter c) to indicate pronunciation

Other hyponyms of diacritic include accent, accent mark, breve, cedilla, circumflex, wedge, macron, tilde, umlaut, diaeresis, dieresis.

diacritic (noun)	hacek (noun)
a mark added to a letter to indicate a special pronunciation	a diacritical mark (an inverted circumflex) placed above certain letters (such as the letter c) to indicate pronunciation

diacritic (adjective)	hacek (adjective)
capable of distinguishing