accent vs stress mark

accent and stress mark both are nouns.

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

As nouns, stress mark is a hyponym of accent; that is, stress mark is a word with a more specific, narrower meaning than accent:

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

Other hyponyms of accent include acute, acute accent, ague, grave, grave accent, double acute accent, Hungarumlaut.

accent (noun)	stress mark (noun)
the relative prominence of a syllable or musical note (especially with regard to stress or pitch)	a mark indicating the stress on a syllable
distinctive manner of oral expression
a diacritical mark used to indicate stress or placed above a vowel to indicate a special pronunciation
the usage or vocabulary that is characteristic of a specific group of people
special importance or significance

accent (verb)	stress mark (verb)
put stress on; utter with an accent
to stress, single out as important