Hungarumlaut vs accent mark

Hungarumlaut and accent mark both are nouns.

Word	Noun	Adjective	Verb	Adverb
Hungarumlaut	Yes	No	No	No
accent mark	Yes	No	No	No

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

Hungarumlaut: a diacritic mark of the Latin script, used primarily in written Hungarian.
accent mark: a diacritical mark used to indicate stress or placed above a vowel to indicate a special pronunciation

Other hypernyms of Hungarumlaut include accent.

Hungarumlaut (noun)	accent mark (noun)
a diacritic mark of the Latin script, used primarily in written Hungarian.	a diacritical mark used to indicate stress or placed above a vowel to indicate a special pronunciation