stress mark vs accent mark

stress mark and accent mark both are nouns.

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

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

stress mark: a mark indicating the stress on a syllable
accent mark: a diacritical mark used to indicate stress or placed above a vowel to indicate a special pronunciation

Other hypernyms of stress mark include accent.

stress mark (noun)	accent mark (noun)
a mark indicating the stress on a syllable	a diacritical mark used to indicate stress or placed above a vowel to indicate a special pronunciation