word stress vs emphasis

word stress and emphasis both are nouns.

Word	Noun	Adjective	Verb	Adverb
word stress	Yes	No	No	No
emphasis	Yes	No	No	No

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

word stress: the distribution of stresses within a polysyllabic word
emphasis: the relative prominence of a syllable or musical note (especially with regard to stress or pitch)

Other hypernyms of word stress include accent, stress.

word stress (noun)	emphasis (noun)
the distribution of stresses within a polysyllabic word	intensity or forcefulness of expression
	the relative prominence of a syllable or musical note (especially with regard to stress or pitch)
	special and significant stress by means of position or repetition e.g.
	special importance or significance